If your nameservers are set to the shared Plesk server you are one then you can log into Plesk to update a DNS record.
1. Log into Plesk with your username and password
2. Select the "Websites and Domains Tab"
3. Select the domain you would like to add a DNS records for
4. Click on "DNS settings"
5. Click the record you would like to edit
6. Update the record information as required and click "OK"
7. Click "Update" on the yellow information bar at the top of the page to apply the DNS changes or "Revert" to discard any changes
