Divide the class into a few groups of no more than 4 people.
Pick one person to become the group leader. This is just for the GitHub repository.
At the top of this page, click on fork. This will create a duplicate of this repository and add it to your account.
Make sure everyone in your team has a GitHub account. Now, in your forked repository, click on settings -> Collaborators & teams. Add all of your teammates and make sure they accept the invite.
Everybody has to clone the repository to their desktop using GitHub desktop (If you prefer a different Git Client or command line you may also use it).
Open the files you just cloned from the remote repository in your favorite text editor or IDE.
In index.html change the ID and text of a person to your name. (Divide the 4 lines between your group so nobody changes the same line)
<div class="person" id="NAME-TEAM-MEMBER-1-HERE">Person 1</div>
To
<div class="person" id="Max">Max 🔌🤖</div>
In style.css below line 31 add a new CSS id selector with your name and change the background to your favorite color.
Open GitHub Desktop and select all the changes you've made. You can select a few lines or the entire file. Give your commit a message that describes what you've changed. After that click Commit to master. After that click Publish branche.
When everyone is done with commiting and pushing their changes, click on Fetch origin after that click Pull origin and watch how all your changes come together in one project.