You paste stuff in there...
--------------------- MERGED ---------------------------
To elaborate, extract the WUD:
Make any edits or ROM hacks you want to do. Hex editing, BFRES editing, etc.
Note the paths on the caffeine_server.exe. It might include /vol/ and other stuff that might not be in the extracted WUD
Paste edits in the right path (MK8 CTs = titleID/vol/content/course/{course name}/)
Then next time you load it, the edits will take place