Log in to your start page for Google Apps which probably statrs with http://start....
When you are on the 'dashboard' page (select dashboard tab if required) you will see towards the bottom left a link 'Sites beta' with the link
Click the blue 'Sites' link and you will go to the Sites Settings page.
Towards the top of this page you will see:-
Your users can access Sites at:
http://sites.google.com/a/cinemapurgatorio.com/ [color=#0000CC] Change URL [/color]
Click the 'Change URL' and then use the radio button to select the custom setting option.
Enter the URL you require and save changes.
You will have to make sure you have a CNAME setting for the address you wish to use.
These are set up via the DreamHost Control Panel under the 'manage domains' page.
On the domains page is a small DNS link to take you to the settings page.
Here you enter the host name in the first box, select CNAME from the drop down and then enter ghs.google.com in the value box.
Then click Add Record Now.
The problem you may have is that you may have added http://cinemapurgatorio.com/ before Google apps was introduced and you will see that it has an A record in the unchangeable part of the DreamHost DNS section. If you added the Domain and added with the Google Apps box clicked when you added it in for full hosting then you should already have an A record pointing to Google for your domain name.
What I tend to do is create a new host (sub-domain) purely for Google Apps where the domain has already been added in to DreamHosts DNS.
So I have something like (where the domain is example.com)
This then has the various Google pages set by me via the 'dashboard' to:-
start.apps.example.com (start page)
web.apps.example.com (web site created with the website builder)
and so on...
You can do this and then set up your page
to redirect to
if you wish.
Opinions are my own views, not DreamHosts'.
I am NOT a DreamHost employee OK! :@
Act on my advice at your own risk!