Here're the steps to create additional admins:

Go to Contacts.

Click on Add New button.

Choose administrator from the Usertype on the left sidebar.

Enter the required fields.

Click on Save button in the top right corner.

On the left sidebar, enable Admin Staff role under the Roles.

Click on Save button.

To send credentials to the new admin, click on Send Welcome Mail button to send the email with login details. Admin has to use these credentials to log in to the dashboard and manage the platform. 

Dashboard can be accessed from here: