Duplicate of this question:
which was correctly answered with this:
"You just need to add an "A" record in the DNS manager on Godaddy. In that "A" record put your IP from dreamhost (the server itself)"
with one difference:
What if there are 10 websites on Dreamhost and i would like to point at a specific website, for example trains.com ?
Instead of creating an A record, i created a CNAME record for my subdomain pointing to trains.com
Yet after propagation, i still get the same result. My subdomain still displays the default plesk page of the Dreamhost server, not trains.com.