You can invite partner users and use the back-office once they're invited to a site. Here's the step by step:
When logged in to the back office, click "General Setting."
Select "Users" to open the dropdown options
Click the users from the list to display all users.
Click on "+Invite User".
Select the "Account" and enter the partner "Email address".
Select Role/s - select the role or access permission for the partner user.
Note: The partner user will receive an email invitation, and they need to accept the invitation to register to access the back office
On the "Invitations" tab are the history details of the invitation sent out to the partner.
Token - is a unique number generated by the back office for each invitation.
Email - the partner email that was invited to the invitation
Registered - a date will be shown once the partner has successfully accepted the invitation and registered the back office
Active - "Yes" the invitation is active or "No" the invitation is not active
Revoke - To revoke the invitation and no longer valid.