Drivers can be added in a variety of ways. If you want to create the account yourself, go to the driver list in the company tab and select 'Add Driver' You will be required to add the driver's name, email and phone number to create an account. After you press 'Save', the driver will immediately receive a temporary password by email and text message. The new driver account will be reviewed by your account executive and approved. After approval, the driver will appear in your list of driver and he can start working. 

Here is a video demonstration of the process: