If you are using a tape library, put it into a slot. In the Devices tab, locate the library. Scan the slot if you are using barcode labels. If you not using barcode labels, right-click on the slot and run a label job on that slot to label the tape.
If you are not using a tape library, put the tape into your tape drive. In the Devices tab, right-click on the tape drive and run a label job
In both cases above, you next go to the Media tab and click on the Scratch media set. RIght-click on the new tape and associate it with the appropriate media set.