Get to the courthouse a bit early. There will probably be a special parking area for jurors. Be sure to use that, and put any placard in your windshield that you’re directed to, or you might get a ticket… or worse.
When you try to enter the courthouse, obviously you can’t have any weapons on your person. You’ll go through a metal detector. You will probably have to surrender your cell phone, so if you’re used to keeping that with you then you might want to leave it in your car (assuming you drive yourself).
After you get into the courthouse there will either be people or signs to direct you to the jury pool room. You’ll sign in and do whatever they tell you to do there, and then sit and wait for a bit.
When most of the jurors have been processed into the pool, there will be an instruction period. This varies from state to state, since (at the state level, which is what I’m assuming), you’ll be instructed on your state’s court system.
After this, there may be a Q&A period, and after that the clerks will start to form jury pools. You may or may not be called. If you’re not called, then you’ll be dismissed after the passage of some time when they determine that they won’t need you.
If you’re called to serve on a jury, then you’ll be following the judge’s instructions in that court.
It can be a fun process. Pay attention and enjoy it.