So, I don't actually recommend diving headfirst into matches. Take a few days, maybe a week or so, and only ever play in Training Mode. The first things you should practice are your pokes and your combos, but there's some other stuff you should check out too: take a look at
my Training Mode guide for tips on how to practice attacks, combos, and more as effectively as possible.
After you've done that, it's time to take your experience to the ring! Unfortunately, if you're anything like me, you'll immediately find that you're suddenly too nervous to do combos and you'll just spaz out and lose. This is, I think, natural! It's just your nerves. From here on out, you ought to be splitting your time between repping your combos, pressure, etc. in Training Mode and learning how to apply them in actual matches.
After your nerves have calmed down, you feel more or less in control of your character, and you can do your character's B&Bs without having to think too much, start analyzing how you move. Movement is actually pretty complicated in airdash fighters; I don't know if you're coming from SF-style games or not, but even if you aren't,
this guide is pretty much all about how to play footsies in GG/P4A/BBCS:EX.
Also, watch lots and lots of videos.