While you can freely develop on the main branch of your fork, it is best-practice to create and develop on a feature branch.
A feature branch is the general term for whatever code you are going to introduce via pull request.
Especially when contributing to a project with lots of contributors, it's important to make your pull request easy to find.
Convention varies when it comes to exactly how to name a branch; however, as a rule branches are named in kabob-case.
Kabob case means all-lowercase-with-dashes-between-words.
As a suggestion, I typically follow something like the following (provided there is no style-guide):
<ME>-<TICKETNUMBER>-<DESCRIPTION>
Suppose I, Eren Yeager, am submitting a feature for issue 3: user input dialog needed!, I would commit all my code in a git branch:
git checkout -b ey-3-user-input-dialogOf course, I would then put the appropriate commit(s) on my feature branch, and push it to my fork.
Try to avoid excessively long branch names.
There's no hard rule on what's too long, so just play it smart.