Dell Precision 340 - Manual (Page 12)

6. If the replacement drive does not have the bracket rails attached, remove the rails from the old drive by removing the two screws that secure each rail
to the drive.
Drive-Rail Bracket Removal and Replacement
7. Attach the bracket to the new drive by aligning the screw holes on the drive with the screw holes on the rails and tightening all four screws.
8. Reinstall the 3.5-inch floppy drive and bracket assembly by gently sliding the bracket into place until the tabs securely click into position.
Floppy-Drive Installation
9. Connect the power cable and floppy drive cable to the connectors on the drive.
10. Close the computer cover , reconnect your computer and devices to their electrical outlets, and turn them on.
Floppy-Drive Cable Attachment