W2K Backup

I have struggled with Removable Storage and how to get the tapes to work with Backup. Can anyone tell me (with no great detail) what the steps are to ready 6 tapes to be used with a scheduled backup that will occur every night. I will use a different tape each night. What do I need to do in the Removable Storage MMC and what do I have to do in Backup to make it work. I keep getting a message stating “the operation was not performed because no unused media was available”. I’ve tried this with tapes in different media pools, but I don’t understand where I’m going wrong. Thanks.