Yo and welcome!
TBH one thing to mainly remember is lots of other players there will also be nervous and it will also be their first time. However yes there will be some seasoned grinders there who are at their calmest whilst at the table.
Do not let this put you off just basically sit down, play some poker and enjoy it! Like anything the more you do it the more it will feel natural.
The main thing is to just follow the action....keep your eyes peeled, listen for the bet sizings and just be ready to act. Nothing worse than someone always forgetting its on them!
Also maybe have a stiff drink