Want real commercial carriers in FSX...

Please forgive my ignorance - FS newb

I want to get some of the real-world carriers paint jobs in FSX (is that called liveries?) I see in many screenshots tons of cool AI planes - Delta, EasyJet, AA, etc... All I have is the stock FSX, no addons or downloads

Are these payware? Or just repaints for stock aircraft? Any good ones or sites to download from that you guys recommend? I want to start small, don't want to add tons of aircraft yet, just want to have Delta, Song, etc... flights in the airports and flying around...

Also, will these let me fly them? And how are they used in the sim? For example, if I install 4 "liveries" if that is the right term, say, Delta, AA, Song, and EasyJet for 737's (just an example), will the AI just randomly populate the sim with these liveries?

If there is a thread or guide out there, please link, I don't mind reading...just couldn't find any real novice info out there and don't wanna mess up my install experimenting too much