Going to my first M tomorrow, what do I do?

I have huge anxiety issues, but I really need to fight them and go to M tomorrow. I'm not Christian and have no devout friends or family, so I'll be going alone. I think I want to become a Catholic - I've been getting what I guess you could call divine impressions that this is something I need to do. Can anyone please offer me any advice? I don't know what to do, and I don't want to offend anyone. All I know is that I can't take Communion. Thank you so much!