When I go to create a Tag in my Contacts list, the drop down shows tags that I didn't make and it won't let me create a new Tag. How do I do this?

If I add a bunch of contacts in the backoffice, what features can I use that don't have an additional cost? Also, it won't let me add tags to my contacts...when I click in the field, there's a drop down with someone's tags in there already but won't let me add my own.