On the Users tab for the tenant, you can manage existing users and add new users.
Your new user will receive an e-mail where they must click the Accept Invite button and fill in their name and set a password.
HINT: If a user should no longer have access to the portal, you can deactivate that user. To do so; click the name of the user, then click X (remove user from tenant).
If you have created a new user and this user has not accepted the invitation e-mail, you can re-send the invitation to the portal.