I don't want to jump on and be the "NAS Police," but if you are "new to these radios," NAS is the LAST thing you should be doing. If you get one small setting wrong, you will attempt to affiliate to the system. At the least, you will likely end up with the radio inhibited or could end up with a visit from a friendly field agent from the FCC, or with computer hacking charges. On the worst end, you could cause a legit user's radio to become not affiliated and miss traffic, or the system not accept their traffic.
If you want to listen, get a scanner. If you want to NAS, you have a long road ahead if you are new to the radios, if you want to do it safely and avoid a visit from nice folks with badges.