Nemoide wrote: I have the manual but it's not too helpful for someone who doesn't even know what "snapping the ball" means.

Your play selection, normally, is probably going to be pretty limited. On defense you’re mainly going to be trying to guess, based on where the opponent is on the field, and the various circumstances in the game, whether or not they’re going to run or pass. If you think they’ll run, pick a play that puts more defenders up in the “box,” which is basically the area near the center of the Xs and Os, near the line of scrimmage, where everyone is lining up. If you think they’re going to pass, you want more defenders out on the flanks, and potentially two high safeties up at the top center of the Xs and Os. If you don’t really know, you might want to just try having a single high safety.
On offense, if you were playing a human, you would want to partly mix up your play selection, run and pass, but in general, on first down you can run or pass. On second down, you may need to pass if you only gained a couple of yards on first down. Third down is a passing down if you’re more than ~3 yards from the marker, or if you don’t really trust your run game. If you can pick up 4 or more yards running, on each play, there’s no reason to stop running, unless you needed to get into some higher level strategy. A lot of your run game is going to be about finding where the defense on the line is weak, and where you can run the ball-carrier through. (There are outside and inside runs, but I don’t really want to get into that yet.) Similarly, when passing, you want to know the routes that the receivers are going to be running, and based on the defense that you see, where those routes will be undefended. Part of that is knowing whether the defense is playing “man” or “zone,” though. If you know basketball, it’s the same basic concept, but if they play man, you just have to look for a receiver who “beat” his defender (got behind him). If it’s zone, there will potentially be pockets where the receivers will be open, that you want to look for.
There are a bunch of procedural rules that probably won’t come up (offsides/false start/illegal shift/illegal formation/illegal man down field) but if they do, I can explain those too.