The Users accounts are complementary to yours. As the account manager, you can invite other people to contribute to your project. They can have access to the Console with a proper briefcase and you can define the functions they can have access to ( read article about the Profiles). You can also define the rights they have on the publications, depending on their roles.
You can manage the Users accounts by clicking on the small wheel on the top menu, then, click on Users.
Create a new user :
Click on "Create User" on the right of the page.
Then, fill the fields according to your user (see example above).
You will need to associate a profile to the new user. To create a profile, read this article.
Then, Save. You have created a new user.
Modify or delete a user :
Click on the pen icon next to the username you want to edit.
Change the fields and Save.
If you want to delete a user, click on the no entry sign icon next to the username.