Agreed the one click installer is definitely the way to go.
3 tips to make the process more enjoyable tho:
1- before you visit the link above go to this one and make sure your domain has been added and is shown as "fully hosted" https://panel.dreamhost.com/index.cgi?tree=domain.manage&
2- The one click page above, doesn't make clear that you can leave the blank after the / in the URL blank. In other words you can install at just http://mydomain.com it doesn't need to be http://mydomain.com/wordpress http://mydomain.com/wp or http://mydomain.com/something else, IT CAN BE LEFT BLANK.
3- Everything takes longer than the panel tells you it will. Especially if DNS propagation is involved. For a friend to test, I added a new sub-domain and added a one click install of wordpress just yesterday. It was a few hours before the DNS reached back to me, it was even longer before it reached my friend. I also noted that some of the panel replies said things like "in the next 10 minutes..." and it was longer than 10 minutes before the panel robot actually accomplished the task.
If your new to this, I would recommend that you do things in 2 steps. Step 1 is getting the domain fully hosted. Once you have done this step, then wait until you can see the dreamhost "coming soon" page at the url. (this might be a few minutes, or it might take overnight). Once you can view the dreamhost "coming soon" page then proceed to the one click installer and you will have wordpress installed in 15 or 20 minutes (most of which is you waiting). If you don't wait for the coming soon page to appear, you will dive into the one click installer then a link emailed to you will fail and you will think something is broken and start changing things when all that is really needed is time for DNS propagation.