How can I add coworkers so I am able to view their CRM and what they re working on?

How can I add coworkers so I am able to view their CRM and what they re working on?

How can I add coworkers so I am able to view their CRM and what they re working on? I am supposed to help our sales people who are out in the field and keep track of their meetings and contacts but it won't let me add them because it says they already have accounts.