How do I add a new User to Magento?
The following video does a nice job of explaining how to add Roles and Users to Magento.
NOTE: You want to give people the least amount of access as possible to your website, especially outside companies who may only be working on one small aspect of your business. Of course, always make sure you use complicated passwords and never share accounts; everyone should always have their own Magento login!
Please let us know if you have any more questions. Thank you.