You have different possibilities.
Use embed
The @Embed annotation allows you to declare pages fragment that can be embed into other pages.
You'll find a full example here : http://code.google.com/p/google-sitebricks/wiki/EmbeddingBricks
Use decoration
The other approach is to decalre a generic page with your header and footer and use the @Decorated annotation on the container div of your page.
Then you have to declare all pages as @Decorated and extends the generic page.
Please find more documentation in sitebricks google group : https://groups.google.com/forum/#!searchin/google-sitebricks/decorated/google-sitebricks/CUOJM-CP9hM/ENe930RAuZwJ