First time flyer, I need some guidance!?

So I'm traveling as an unaccompanied minor(17)&I was just wondering exactly what I do at an air port when I get there...&I already bought the ticket online, so I assume I'll just bring those with me! Anyways, I have the basic idea, arrive early>check in(what do I actually do here? show them the papers I printed i guess)>after that I think they give me my boarding pass and some tags for my bags if I am putting it in the cargo>check in the bags if going cargo or just go through security with a bag im carrying>then after security, i should be at the areas with the gate!..Sorry the list was so long, i just want to be 100% sure.&I have a connecting flight at Phoenix, how do I go with that? It's a 4 hour connecting time, hopefully it changes! But anyways, what do I do there? Do I have to check in and if i do, should I just do it immidiately and hang out by the gates?! thanks!