Thought maybe I could help you, but I have a BC785D and I don't know if they program the same way or not.
Basically what you have to do is select a bank and set it for Trunked. Then enter the frequencies for the system. With mine you don't have enter Text Tags for the frequencies because when the frequencies appear on the screen you don't see the tag information.
After you get the frequencies in you will enter the talk group ID numbers for the talk groups you want to listen to. You will want to put the text tags in for the talk groups as they will appear on the screen when the active talk group ID appears. Also make sure the unit is in the ID SCAN mode. That way you will hear only the Talk Groups you have programmed in. If it is in the ID SEARCH mode, you will hear all actrive Talk Groups in the system whether or not you programmed them. It tells you how to put the unit in the different modes in the manual.
Motorola Type systems are the easiest to program because all you need are the frequencies and talk groups. No fleet maps, base, or offset frequencies or spacing.
In your manual go to the Trunking section and it will explain what you have to do when entering the frequencies. Then there should be another section about Talk Group ID Tags that explains how to do that. You may have to read it a couple of times if you're not familiar with trunking. Just take it slow, one step at a time. When I did mine, I had never programmed any trunked systems before and figured it out. If you have a problem email me. Just click "EMAIL" on my post and send your message and I'll try to help you there, rather than take up a lot of space here. I'd be more than happy to take the time to do it if you have a problem.