Hi ms_NightBlade!
You can join our jam using one of your or your friends' itch.io accounts. Alternatively, I guess you could create an account representing your group and use it if you prefer.
Either way, when you submit your game, you will see a short form asking if you worked on it alone or as a group. If it is as a group, it will also ask for usernames associated with the group.
I hope this helps. Please let me know if you have any other questions or need more clarification. Thank you!