Search for register a trade name and/or trademark xx. xx = your state abbreviation.
1. I searched register a trade name and/or trademark az.
There is great info at that link, forms, handbooks etc. Do not pay for someone to do this, it is like for $10.00 if you fill the forms yourself and send them it, do not get scammed I have seen some companies offer to do it for like starting 199.00 special for 3 days only , blah blah blah,
Your state might have some of the same links.
The website up there has the links for the us patent and trademark office also.
Hope that helps. Send me a note if you have problems finding it for the particulars in your state.