To add additional users or locations to your account, click on the "Users" tab:
Then click on the "+ Add User" button:
Fill out the form that has opened up. Make sure the Timezone is set properly to ensure Schedules and Messages play back at the right time.
The User Type determines how much control the user can have. A User is able to select which playlist/mix/schedule they would like to hear. User (No Channels) is for streaming only. Select the User (No Channels) option for a top down management operation of the account.