Your manager can enable two distinct ways of seeing your co-workers' schedule. Both settings must be activated by your manager in order for you to have access. You can either see who's working at the same time or see the full schedule.
Who is working at the same time
You can see who's working at the same time simply by clicking on a shift
See the full schedule
Go in "My schedule"
Click on "See coworkers schedules"
Go to "Schedule"
Click on "Full schedule"