To be able to create project groups, you must be the owner of the project.
By default, all collaborators are placed in the same group ("Main group"). If you would like to organise your project collaborators into custom groups, you can define groups and assign your collaborators to these groups from the Collaborators page. Collaborators can be given permission to access data from collaborators within the same group (see "Set permissions"). If a collaborator is part of several groups, they will have access to data belonging to all of the groups they are part of when given access to group-level data.
Click "+ New" and select "New group"
Give your group a name
Choose from the dropdown menu which of the collaborators in the project you want to assign to the group. (You can also leave this space open and come back and assign collaborators later) If your collaborator is already part of a different group, they will be added to the new group as well, without being deleted from the previous one.
Click "Create"