Go to your account settings page.
Under the Account tab, you'll see the Profile column and at the bottom you'll find both a +Cameras and +Lenses buttons. Here you can add your camera and lens information.
If you would like to edit your current gear, simply click on the text box and type the new information. If you would like to delete an entry, click on the text box and erase the text in the box.
Once you are happy with the new details, click on Save changes at the bottom of the page.