If you want to share your code over GitHub with your project partner you'll need to pick between the two of you whose copy of the starter code you want to work off of. For example, if users
JoeBruin want to collaborate then they might both choose to work off of
sp21-proj2-OskiBear. In that case
OskiBear would navigate to "Settings", "Manage access", then "Invite teams or people" and add
JoeBruin(see images below).
JoeBruin should receive an email afterwards containing an invitation to the repo. Alternatively
OskiBear can share the link to the repo after sending the invitation.
Once you both have access to the repo you your partner can clone the repo to get a local copy to work off of. From there you can share files over git, pushing and pulling updates as you collaborate. Do not add anyone other than your project partner to your repository. You aren't allowed to share code with any students other than your project partner for this project.
After following these steps your partner should receive an email containing an invitation link. Alternatively, you can share the link to the repo with your partner.