If you already know how to use the basic Github workflow, you don't need to read further.
Find something to work on. Whether this adds a new feature or fixes something, make an issue first (or find one).
Join the discord server. This helps with collaboration and communication.
If you don't know how to use basic github CLI, work on that.
After you make that issue (or don't it's totally fine), then start working on your code. The code will be in a fork of the repository that you make. To make a fork, press the fork button above the about section in the repo:
After you feel like your idea is somewhat presentable in code, make a PR in the Pull requests tab above the repository:
(It's the third tab)
A pull request is the thing that allows you to pull your code into the main repository. It also allows other contributors to edit your code so that it'll be well refined once pushed.
Make changes that are needed to the pull request by maintainers. & just wait for it to be added.