If the client is registered on the 1b.app website, you can give him access to the
https://1b.app/ua/contact-access/ section by adding the client as an administrator. In this case, the client enters by ID. Those. enters his phone number and receives an SMS code. In subsequent times, you can enter by phone number and SMS code
If there is no need to add the client to the admins, then write the password and login in the Box in the Access Rights