There are two ways. The easiest is to go to the mailing list page at http://www.gnome.org/mailing-lists/index.shtml. Click on any of the list addresses on the left, you will be able to browse the archives of that list.
If you need to search the archives, you can use the request address for that list. One of the emails it sent you when you first subscribed gives instructions on how to do this. If you have lost those instructions, email firstname.lastname@example.org with a subject of archive help. It will reply with instructions on how to use the archive system.