1. Preparing the toolDownload jBS2BG and extract archive to any location.
Optionally, download the images archive, these images can be useful for assigning morphs to NPCs, so that you know who's who.
Of course, NPCs that don't have images won't show up in the Image View.
Extract the images archive to the same folder as
jBS2BG.jar, it should look like this:
2. Setting up base bodyBodyGen needs a base body with morphs enabled to function.
Using BodySlide, set the preset to
-Zeroed CBBE- and generate your base body with
"Build Morphs" enabled.
Generated files should go inside
"Data\meshes\actors\character\character assets".
The folder should now contain the following files:
"femalebody_0.nif",
"femalebody_1.nif" and
"femalebody.tri".
Your
"Data\meshes\actors\character\character assets" folder should look like this:
3. Setting up replacer clothes and armorsFor BodyGen morphs to be visible on clothed characters, you need outfits with RaceMenu Morphs.
You can find several outfit mods with morphs support across the net, here are some:
Vanilla Outfits BodySlided (includes armors and town clothes)
OCR - Omnisway Clothing Replacer - CBBE BodySlide BBP TBBP (includes fine clothes, jarl clothes, wedding dress...)
The Provocateur's Armoury (includes mage robes, monk robes, necromancer robes...)
Build these outfits with the same slider settings as the base body, in this case, use
-Zeroed CBBE- preset.
You also need to build these outfits with
"Build Morphs" enabled. You'll know you have morphs enabled if you get a
"*.tri" file next to the output
"*.nifs".
There are instructions on those pages on how to build them. Please read and follow them carefully if you have no idea what you're doing.
The files you've built should be used as replacers, for example, your
"Data\meshes\clothes\farmclothes01" folder should look something like this:

Those .nif files are the meshes built from BodySlide, including the .tri file, which contains the morph data for RaceMenu.
4. Enabling BodyGenWith RaceMenu installed, go to
"Data\SKSE\Plugins" folder, open the file
"nioverride.ini" and ensure that
BodyGen is enabled,
bEnableBodyGen=1, like this:

This will enable BodyGen in the game.
5. Using jBS2BG to convert BodySlide XMLs to BodyGen templatesUsing the tool is pretty straight-forward.
Make an XML preset in BodySlide of the body type you like and use
"Save As..." to save it somewhere as XML.

Launch
jBS2BG.jar, then click
"Add BodySlide XML Presets" button then locate and add the XML that you just saved from BodySlide.

After adding, you can now see the BodyGen equivalent of the XML preset that you created.

By default, the resulting template will use the Big values, meaning, the max weight of the body you created.
This can be changed by using the
"Edit SetSliders" button. With it, you can pick the weight to use or even use range between Small(Min) and Big(Max).
6. Using jBS2BG to assign presets to custom targets like "All Female NPCs", "All Female Nords"... etcNow that you have a preset in your list, you now have to assign it to some NPCs.
Now then, go to the morphs tab:

Say you want to assign your preset to all female NPCs in the game.
In the Custom Target text field, type in
"All|Female" (without the quotes), then click the
"Add" button just below the text field.

When you have some presets in the list, a random preset will be automatically assigned to a newly added target.
Assigning more presets to the
"All|Female" target will make BodyGen pick a random one from the assigned presets to morph the target.
For assigning morphs to specific races, you could use something like
"All|Female|NordRace",
"All|Female|BretonRace", etc...
7. Using jBS2BG to assign presets to NPCsNow, say, you want to assign a preset to a specific NPC,
First, you need a text file containing a list of NPCs to be added. You can generate this using the included TES5Edit script in the jBS2BG folder:
"jBS2BG Export NPC List.pas".
If you don't have TES5Edit, at the moment, you can just use the one included in the jBS2BG folder:
"FemaleNPCList - Dawnguard + Dragonborn + HearthFires + Skyrim.txt".
To generate a list from TES5Edit, copy the .pas script into your
"Edit Scripts" folder.
Right-click the Master/Mod that you want to get the NPCs from (You can select multiple Masters), then click
"Apply Script".

Then select the script
"jBS2BG Export NPC List", then hit
"OK".

Wait for the export process to finish, this process might take a while for Masters with tons of NPCs in them.
After it's done exporting, you can find the
"*.txt" file in the same folder as
"TES5Edit.exe" or your Skyrim installation folder.
With the text file exported, go back to jBS2BG, now click
"Add NPCs", then
"Add NPCs from File", locate and select the text file containing the list.

Now you can browse the table and select an NPC you want to add. To add one to the list, select the NPC then click
"<= Add".

You can click on the table headers to sort the list and you can also right click on the headers to filter the list.
8. Generating and exporting the INIsYou can simply click on the
"Generate Templates" and
"Generate Morphs" buttons to generate the content needed for
"templates.ini" and
"morphs.ini"which you can copy and paste to the respective INIs.
But an easier way is to go to
File -> Export BodyGen INIs.

After that, both
"templates.ini" and
"morphs.ini" will be exported to your chosen location.

Now, put both
"templates.ini" and
"morphs.ini" inside the folder
"Data\meshes\actors\character\BodyGenData\%MOD_FILENAME_WITH_EXT%\".
Where %MOD_FILENAME_WITH_EXT% is something like
"Skyrim.esm", let's just use
"Skyrim.esm" for example,
"Data\meshes\actors\character\BodyGenData\Skyrim.esm\".
Finally, you should have:
"Data\meshes\actors\character\BodyGenData\Skyrim.esm\templates.ini"
"Data\meshes\actors\character\BodyGenData\Skyrim.esm\morphs.ini"And... that's it! Fire up the game and enjoy!