Go to the DNS settings by selecting the DNS tab at the top of the screen.
Once here, you will want to add a CNAME record. For example, if your website is www.domain.com, the record should be added as:
CNAME www is an alias of ghs.googlehosted.com
Note -- Please confirm the record values that Google wants you to use. The above is just an example to show the proper formatting in your DNS settings.
For instructions on how to configure a redirect for your Google Apps domain, please see the article on URL forwarding. --> http://support.google.com/a/bin/answer.py?hl=en&answer=61057