Suppose your domain is example.com and Faqprime based knowledge base URL is https://example.myfaqprime.com, which is it to be known as https://help.example.com.
Here is the complete instruction set -
Get the secure proxy URL from FAQPrime team i.e. secure1.myfaqprime.com or secure2.myfaqprime.com...
Login to your Domain Control Panel
Go to the section which says DNS or Name Servers
Create a new CNAME record with name/host/alias as your custom support URL pointing to secure proxy URL i.e. secure1.myfaqprime.com or secure2.myfaqprime.com.
TTL: Enter a Time To Live between 30 minutes to 1 hour, or leave this field in its default settings
Save changes to your DNS records.
Inform FAQPrime team, now FAQPrime team shall generate the SSL and do the setup.