To assign a representative to a project, you will need to be an admin user for your company.
Step 1: Find the project in the "Projects" tab.
Step 2: Click the "edit" button as shown below, under "Solar Representative". A list of your company's users will pop up. Select the user(s) that you would like to assign, and click "Done":
Process complete! That representative will now be able to view the status of and upload documents for that project.