First, login to google admin: https://admin.google.com.
You should then see the following dashboard. We have already added the appropriate domain to our account, so we can go right into adding email accounts. We do that by going to Users.
On the Users screen is a yellow + button to add users. If you hover over that button, you will see there are options to either add a single user manually, or you can upload a CSV file to bulk upload email accounts.
For our project, it makes sense to do a bulk upload since we are adding quite a few email accounts.