Here's a link to part 1, of a video course...
https://pickleballcommunity.com/new-to-pickleball/
Or you can browse YouTube for many introductory courses.
A few things you need to know:
How to keep score. It's a tad confusing for beginners, but you'll get the hang of it.
Etiquette:
Don't open the gate while a point is being played on the court next to the gate. Wait until the point ends then enter.
Don't cross a court while a point is being played. Wait until the point is over.
When your ball rolls or flies toward another court announce "BALL ON COURT!", this is so nobody steps on a ball and hurts a leg or foot.
Play within your skill group. Don't be the Beginner, or Advanced Beginner, playing in the Intermediate or above group, and be the person who ruins every point because you can't return the ball. There is a group for your skill level. Please find it, and gradually try your game against stronger groups, but be prepared to move out if you are not capable of keeping the point going.
Learn the kitchen rules. Again, there are lots of videos on YouTube on the kitchen rules.
Kudos to you for trying to get into the PB101 classes, but if they don't have room for you, you don't need to stay away from the courts until they can accommodate you.
You, in all likelihood, have a friend or neighbor who can introduce you to the basics of court etiquette, scoring, kitchen play, and give you some tips on getting your serve in, the "3-Bounce Rule", and other basic elements of PB.
Here are some more links to excellent YouTube videos on getting started in PB
https://www.youtube.com/watch?v=xEYsymCtIDY
Have fun. 99% of the picklers in TV are open-armed, welcoming people, happy to help new players. There are a small number of players who are nasty to those who mis-step, but they are easily ignored. If you happen to cross one of them, don't let it deter you. You will soon learn they are a tiny minority.