Version: 2021.3
Step 1: Get a Bitbucket account
Step 3: Clone your fork

Step 2: Fork the repository you want to contribute to

This demonstration uses the Unity Test Tools Repo.

There is a sidebar on the left-hand side of the repository page, with an Actions section:

Click the Fork button and fill out the form you are redirected to, then click Fork repository:

When you have finished forking the repo, you’ll be taken to the landing page for your new fork:

Step 1: Get a Bitbucket account
Step 3: Clone your fork