Here are the steps to create and invite a friend to a group (= invite a friend to your room):

Go to your profile and click on the “Group” link in your reservations.

You can then create a group with the button on the left.

You are now the owner of a group and can see all the information about it.

You must now copy the invitation code and share it with your roommate.

Here are the steps to join a group:

Go to your profile and click on the “Group” link in your reservations.

Enter the code given by your roommate in the “Join” box and then click “Join.”

You will now see the complete group; you are guaranteed to be together in the same room.