Install WP on a redirected domain?


Hello, I’m volunteering to re-work a web site for a local park, we want to use wordpress, and there is an existing site on a .mac account.
I moved the hosting for the park’s .org site to Dreamhost, and set up the domain to redirect to the .mac site.
Can I install wordpress and start building the new site, test it etc before “flipping the switch” on the .org address?
When I try a wordpress install, the domain doesn’t show up in my list of hosted sites, I’m assuming because it’s not hosted yet, it’s redirected.