To edit contact info, login to the MSPControl and click on Contacts,
or go to Organizations > Exchange > Contacts.
You will see the list of all existing contacts. If you have many, it might be a good idea to use Search form in the right to find the one you need. You can choose whether you want to search by Display Name or E-mail Address.
Once you found the contact you were looking for, click at them.
You will see two tabs, General and Mail Flow Settings. Let's take a look at General.
You can select whether you want to Use MAPI rich text format
Next, you can decide if you want to hide this contact from address book and enter personal details.
Finally, you can add even more company and contact info, as well as physical address. None of the fields are mandatory. To show / hide sections click on their names or "+" / "-" icons in the right.
When you're done here, click either Save Changes or Save Changes and Exit. The first option will leave you at this page, the second will redirect you to the list of all contacts.