I've extracted the .bsa file with OBMM into the Data folder (overwriting some things, I think), I've put the whole .bsa file, and the .esp and .esm files in there too, and the esp/esms show up in both OBMM and Data Files in the Launcher…
Still, I'm afraid that I did something wrong. How can I know it'll work properly?
Best Answer
By starting the game and looking around.
Oscuro's Oblivion Overhaul is a pretty freaking huge change, there are many new enemies to fight and a lot of new armor and weapons to find. You should be able to tell in a few minutes that the new stuff is there.
That, by the way, is just making sure everything is installed correctly if the game doesn't tell you right out: If you find float exclamation marks, checkered purple/black textures or the game just right out crashes you'll also know you didn't install it correctly.