Instructions
Download and install the Fallout Mod Manager. This is a one-of-a-kind program designed to manage the mods you install for "Fallout 3," along with other functions like unpacking BSA files.
Launch Fallout Mod Manager. Wait a few minutes for the program to fully load.
Click "BSA Unpacker," followed by "Open." A new dialog box will appear.
Double-click the BSA file you want to unpack to automatically import it into the GECK.