In order to add a "Service Contact" to the case you will need to do the following:
1. Click on the orange "Action" button.
2. Click on "File Into An Existing Case".
3. Select the location your case is in.
4. Enter your case number.
5. Click "Search".
6. Click on the black "Actions" button.
7. Click on view service contact.
8. Find the party you want to add the service contact to.
9. Click on the black "Actions" button to the right and click on Add New Service Contact, enter your name and email, press Save Change.
10. You can also click on Add from Firm service contacts if using a Firm Account and select the email contact for service. To learn more about the Firm Service Contacts list, click here.
Once you select the service contact you can click close and they have been added to the case.
For further reading: