Additional users can be invited into myplan. Inveited users will have complete access to myplan.
To invite additional user in myplan, click on settings > user settings > user management
By default registered user will be created as primary admin in user management. Any additional user created in myplan it will be created as secondary admin. To create additional user click on create which is located in top right hand corner and a pop window will open. Enter the user name and email and click on save to add the user.