Select the customer option from User Role and set the limitations from Role Matrix.
Set Invite and the user will receive the info and be added to the project.
The user that has limited access to some sections won’t be able to perform several actions. For example, if you don’t allow it, a user can’t use Quick Research and it will be disabled from that specific project.
In case you are a user to multiple projects, you’ll have to select the project you want to work on. You can switch the project you want to work on when you log in or from Settings - Switch Account.