Your BGO is typically assigned based on your h.s. -- each BGO covers one or more schools. If you really want to know who your BGO is now, you can try asking your college counselor, you may know.
Once you are in the Candidate Information System (CIS), you'll be informed who your BGO is. I believe candidates are entered into the system -- i.e., you have access to it -- around May 1 or June 1 of you junior/rising senior year.
If you're a junior, there really is no rush to contact your BGO at this point. He/she can't yet do your interview as you're not in his/her system, you aren't an official candidate, etc. If you have specific questions about USNA, you might want to seek him/her out, but you can probably wait on those questions until May/June.