You can add a new user to a file by clicking the tab 'Users' in the menu 'settings'. Click 'Add' in the top right corner. Every additional Billit user is 5 euros extra per month.
Fill in the email address at the top. You can now assign rights to the user. Move a switch to the left to disable that right. If you do not change any of the switches the user will have all rights. Click 'Save' at the bottom of the page.
After you save the email address, there are two options.