To give the moderator profile to an existing user :

1- Go to Control Panel

2-Click on Users and Organizations

3- Click on the "dots" button to have more functionalities

4-Click on Edit

5- On the dashboard about the user you selected, click on Roles

6- On the roles dashboard, click on the button "Select"

7- Choose the role portal content reviewer to give to the user the moderator rights

8- Save your modifications