To do this, go to "Contact person" in menu

With the button New contact person you can create a new contact.

In this mask the following fields are mandatory:

First name, last name and email address.
The email address is the most important thing, as it also controls access.

You can also assign their roles/functions to the contact for a better overview.

In the Project Access tab, you can control whether a contact gets access to the plan management or not.
Here you also give this contact the predefined permissions.

If you set the slider from "Create Project Access" to "YES," you get a selection of functions.

If the contact (email address) is not yet registered as a user or guest in your tenant, you can do so via the first function.

All you need to do is click on "Invite users as a guest."
As a result, the contact is automatically created in your tenant as a guest and also receives an invitation by email.
Via this invitation, the contact must register from the tenant according to your specifications and then only gets access to this SharePoint page from Plan Management.

With the second function you can then assign the rights to the contact what he can do on this page.

Here are the predefined three roles:

1. Visitors:Only approvals and contact persons can read this role.

2. Member:Only read approvals to this role and create contact persons (do not give project access)

3. Member and fee:This role may see plans submission, advance and approvals. Create contact persons (don't give project access).

If they "Member and submit," another permission (detail field) is unlocked.
Here it is then controlled what this contact may give in.