I've been granted an FCC license for a GMRS radio (ZA category), which I use
in my business, and found on their website that my call sign is... WQCTxxx.
It is a seven character combination or capital letters and digits.

What does it mean and how can I use it? My "radio" is a small handheld
walkie-talkie with 4W max power output. Where is the call number in there?
Shall I use it when I talk to my counterpart: "Hello, this is WQCTxxx,
please, report to me?" Is it all to it? Like a caller ID only in the air?

Is there a set of rules describing the proper use of it?

Thanks