Yes, you can add users as administrators to your app account. Administrators will have complete access to the account's dashboard, and will have their own login email and password. To add administrators, click the "Settings" tab (the gear icon) in the main menu. You'll see five buttons across the top of the screen; select "Account Administrators." Click "Add Administrator," and fill out the form with the user's information. Later, you can edit their login information or remove an administrator by clicking the pencil or the x icon next to the person's name.
If you're looking to add a new user (without dashboard access) just to the app so they can request reviews, please see this article.