Forum / links Question

I setup a forum

the address is www.philshopper.com/forums

how can i change this to forums.philshopper.com?

i am new to this hosting thing i dont know anything so please
be patient with me. thanks for the help gurus

Add forums.philshopper.com as domain and set it to redirect to www.philshopper.com/forums

https://panel.dreamhost.com/index.cgi?tree=domain.add_domain&

happylittlethings.com

thank u so much!