Click on the Onboarding Icon (Red Rocket). 

Click "People" located on the red subway map at the top of your screen.

Tip!
If the role is already created, you can select it from the group of roles indicated on your screen.

Locate the role from the available selection and click on the "Assign to" tab to view the list of users.

Select the name of the user to apply him/her to the role.

The user will now be correlated with the selected role. Users can also be given more than one role. 

Assign a Role to a User