A Computer Case usually has three or four half-height drive bays. Use one of the bays that has a removable face plate that will allow outside access to the floppy drive.

Snap the face plate out of the bay that the floppy drive is being installed in.

Then slide the floppy drive into the bay through the front of the case. Make sure the floppy drive is oriented correctly. The eject button should be on the lower right hand side of the floppy drive.

Fasten the floppy drive into the case by inserting screws through the drive cage and into the floppy Drive. You should find holes along the side of the floppy drive specifically for this purpose.