If you have permission to access the list of Portal Users, you can click on More / Portal User. Once that screen loads, click Create new user to get started.
Notice that there are 2 tabs – General and Permissions. Fill out the names, email and initial password in the General tab.
In the permissions tab, first select a Permissions group. The permissions group will set which sections and actions this administrator can have access too.
Then set the teams for which this portal user will have access.