Hi Emma. Gameplay launches on the 14th, so not long now.
Those currently playing are beta testers. The only way to be a beta tester is to have bought more than 500 booster packs. If you want to trial a specific team; take a look at @holoz0r's gameplay streams and message him there to make a request and watch it play out.
See you on the field :)
I'll be doing my next live stream in just over a week's time! :)