I'm assuming it's a combination precinct-mtg/convention like most small counties have.
You walk in, look for a registration table for your precinct, and sign two forms. One is the precinct attendence and the other is the delegate credentialing sheet. Check off county, district, and state conventions on the delegate sheet.
At some point the county chairman will call the convention to order. He makes a motion that "All present here today shall be elected to the subsequent conventions as delegates". Everybody says AYE, and it's over. Then they forward the paperwork to the state and the district convention. If there is any problem with your credentials you'll get a letter about it.
There will probably be some local politicians there handing out literature and shaking hands ... and some reports by the county party officers. Not much really "happens".