Before you start, lay out all of the parts and tools you'll need. You may want to use a clean white sheet to do this. That makes it easier to spot small items, like screws, and helps keep things from rolling around and getting lost. Make certain that everything you're supposed to have is included with the drive.
Most drives come with the proper data cable and power adapter.
However, if your tape drive hooks up to a SCSI adapter card, you may have to buy that separately. Check the unit's box or the installation manual. They will generally state what's included. Your dealer can also give you this information. Although the installation procedure is very straightforward, you should read the installation manual before you begin.