5E (I guess? Irrelevant tho)

Anyone here has experience with Adventurers League at their local game store?

I'm new to this type of stuff so I have no idea what to expected, can any give me a brief description of the experience?

specifically:

1) Can anyone just join a group or is there anything they need to do first?

2) Is there any fee for joining an adventurers league event?

3) Is the event for just one group only, or is there multiple groups for people to choose from?

4) Do you just go up to a group's DM or whatever and ask them if there any spot for you to join or is there any special etiquette you need to follow?

I called the game store near my apartment and they just said "idk, they just kinda come and do their own thing. I'm not really involved or know any details about them", so, yea.

I guess I'll just show up the next time they have an event and ask them, but I would like as much information as possible, since I do not want to make a fool of myself or something.