I would suggest you navigate to "Manage Domains" in the panel and add a new subdomain called something like "mytest.jerrygrasso.com" (or whatever sub domain name you like). You can accept most of the defaults there except the first two.... For "Do you want the www in your URL?" my preference there is to change it to "remove WWW"... just don't set it to "leave it alone" that setting leads to confusion. The second thing you will want to change is the "Run this domain under the user:" drop-down. Make that say "Create a new user" and then in the box that appears supply a new user name. (this helps keep your experiment in an entirely separate space from your current site.)
Step 2: WAIT. Wait until you can visit mytest.jerrygrasso.com (or whatever you named it above) and see the default "dreamhost coming soon" page. If you don't wait, what will probably happan in the next step is you will get emailed a link that doesn't work yet, and that will confuse you.)
Step 3: visit the one-click install section of the panel. https://panel.dreamhost.com/index.cgi?tree=goodies.installer& and install wordress. Again you can accept the defaults for everything, the only thing you need to make sure you get right is the dropdown for where you want it installed, which will show both jerrygrasso.com and mytest.jerrygrasso.com as well as any other domains on your account. (hint: you can leave the box after the / blank).
Now you will have a separate wordpress development site. When you are ready to move that site to your main site come back and ask if you don't yet know how to do that.
Good luck! Anymore wordpress is pretty cool, and it's pretty easy to install for anyone now.
PS--- The "wait" in step 2 might be just a few minutes, but could be 12-24 hours. (DNS Propagation)