I already have purchased the white-label of the app, so will I be able to mask the url as well with the vanity URL? So the url will be like http://mycmsname.myvanityurl.com.
It allows you to nominate a DNS hostname, which you already own/have control of.
You would create a DNS CNAME record pointing that name, to our servers, and we configure our servers to accept traffic for that URL, and have SSL certificates issued to suit.