I would like to add rules to my pages similar to this example:
http://frenchwomendontgetfat.com/food_and_wine

Thanks in advance for your help.

Hi.

Do you mean keeping your page content or objects centred?

If not please clarify.

Cheers,
Tonga.

If you mean the horizontal and vertical lines decorating the page, one way is via the main menu Object > Shapes.

There are also buttons you can add to your toolbar (right-click the bar) that will give you more direct access.