Usage:
Download and copy in d3d9.dll from the ENBseries package for Dark Souls 2 available on the ENBseries website.
Copy the contents of this archive into your game's folder alongside the DLL.

On GeDoSaTo:
You can use GDST for texture replacement while ENBseries is activated! Simply add
interceptOnlySystemDlls true
to your GeDoSaTo_user.ini file and disable all effects. No SSAO, DoF, bloom, or postprocessing from GDST can be used.

On Performance:
I get a solid 60 FPS with AO turned on at 2560x1440.
At 3840x2160, though, I can only hit 40 without disabling AO.

Notes:
Some types of lights cannot be changed by ENBseries, and as such, might look weird. 
A good number of areas have portions in them that are FAR too dark. So far, I haven't been able to fix them without ruining other areas. Try torch or Shift-F12 required ahead. 
You can enable a high quality film grain shader by uncommenting #define ENOISE in effect.txt. You can also disable the sharpening effect by renaming effect.txt.
You can disable the lens flare effect by disabling EnableLens in the in-game configurator, or enbseries.ini.
Make sure to copy over the ENBseries folder, or some effects will appear incorrectly.
This won't work with the DX11 version, unfortunately. Maybe in the future someone will figure out how to replace the shaders in it!
If you want to test different ENBseries presets, a good practise is to drop the effect files in a seperate folder and symbolic link them to the main DS2 directory.
Did you know XHB is the abbreviation for cross-hotbar? Did you even care?

Credits:
Boris Vorontsov, for creating ENBseries. 
wickfut, for his original preset, which was used as a reference.
CeeJay.dk and everyone else who's worked on SweetFX for sharing their excellent work.
Marty McFly and everyone who's worked on MasterEffect for sharing their stunning work.
HeliosDoubleSix for allowing useful code from their Skyrim ENBseries to be used elsewhere.
kingeric1992, for the really cool lens flare and depth of field shaders!
And everyone else for lighting the way.