On primary voting day in your state and after the polls close at 7:00 PM, you will attend your neighborhood precinct meeting, usually announced on the door signage at your voting location, and usually always in the same building.
For example we vote in school houses here, so after 7 PM, a room or gym, or cafeteria is available and set up for the precinct meeting.
At your precinct meeting you will get to vote on a few things, like electing a chairman for your precinct, (maybe you want to nominate your spouse), and you will hear when your county convention is scheduled.
Volunteer to be a delegate to your county convention. Then the slate of volunteers is voted on for the certain number allowed for your precinct.
At the county convention you will develop amendments for your state convention platform and vote on different motions, and also hear the details for your state convention.
AT the county convention you can volunteer to be a district delegate to your state convention (3 days) and this slate of volunteers will then be voted on.
At STATE convention you can be sent to the National Republican Convention as a state delegate, or alternate delegate (who shares the floor time with the delegate).
Expenses are for travel, special room rates at a nice hotel and meals.
Call your county Republican Party office if you have questions, and you can look up county, state and national convention details on the internet, I bet.
Good luck!!
Thank you for the information.