If you would like to change the permissions of an existing user, hover with your mouse pointer on the gear icon, top right side of the screen, then click on the Settings → User → Edit. You can also remove a user by clicking on Delete option, below the Edit.

Once you click on Edit option, you can choose 3 options under User role tab. Once you decide the role for that particular user, click on the green check mark to confirm your decision. The same action can be canceled by selecting the red x mark.

Note: You can also decide to make another user the owner. Once you have clicked on this, this person and the email address provided will be the only ones with the authority to make another user the owner again. So please make sure to double-check this! At the same time, only the account Owner has the permission to add or modify these roles.