To install .ba2...

Copy & Paste the MapVendors.ba2 and MapTouchUp.ba2 files into the Fallout 76\Data directory.
Default install location
C:\Program Files (x86)\Bethesda.net Launcher\games\Fallout 76\Data
Your game installation may be different if you chose a custom location before downloading the game

Now copy & paste the included Fallout76Custom.ini into the directory below.
C:\Users\YourComputersUsername\Documents\My Games\Fallout 76
or
Edit in MapVendors.ba2 and MapTouchUp.ba2 to your already created Fallout76Custom.ini

[Archive]
sResourceArchive2List = SeventySix - 00UpdateMain.ba2, SeventySix - 01UpdateMain.ba2, SeventySix - 00UpdateStream.ba2, SeventySix - 01UpdateStream.ba2, SeventySix - 00UpdateTextures.ba2, SeventySix - 01UpdateTextures.ba2, SeventySix - MeshesExtra.ba2, SeventySix - 02UpdateMain.ba2, SeventySix - 03UpdateMain.ba2, SeventySix - 04UpdateMain.ba2, SeventySix - 02UpdateStream.ba2, SeventySix - 03UpdateStream.ba2, SeventySix - 04UpdateStream.ba2, SeventySix - 02UpdateTextures.ba2, SeventySix - 03UpdateTextures.ba2, SeventySix - 04UpdateTextures.ba2, SeventySix - GeneratedMeshes.ba2, SeventySix - StaticMeshes.ba2, SeventySix - 05UpdateMain.ba2, SeventySix - 05UpdateStream.ba2, SeventySix - 05UpdateTextures.ba2, MapVendors.ba2, MapTouchUp.ba2

To install Loose file...

I, myself, have never used loose files.
If you're looking for a loose file to install with, then you probably already know what you're doing with them.
Sorry