Disregard this content of you are well verse in the word of making a website. But if you are need step step guide on how to set up a subdomain on dreamhost, it is the right place for you. I assume you know already what is subdomain and domain name.
1. Log in to your dreamhost cpanel
2. Click the manage domain at the leftside
3. Inter or input your desired subdomain name, ex. subnew.domain.com
4. Click the fully hosted
5. Click one click install at left side of cpanel
6. click the wordpress
7. Click customize installation
8. Select your newly created subdomain name.
9. select automatic create database
10. then, you see the the success
11. wait for 10 minutes and check your email for the complete details.
Good luck hope you understand this simple guide.