You can add DNS records on your Plesk panel by following the steps below,
Login to your Plesk Panel using the URL https://yourdomain.com:8443 and click on “Domains” to list them.
Select by clicking on the domain name for which you want to make the DNS changes.
Then click on “DNS Settings” under the “Web Site” tab.
To add A record, click on “Add Record” and to edit any entry click on DNS record.
You can select the record type (A, CNAME, MX etc) from the drop down box.
Enter the required details and click on OK.
The changes will not saved automatically after you click on OK button, you need to UPDATE after saving the changes. It will take about 4 to 5 hours to complete the propagation.