Setting rights at the pages menu will allow you to both set rights for one page but also allow you to push rights down to all subpages.
- Navigate to the page you wish to set rights.
- Click the Live edit button
- In the properties tab select Permissions.
- Select the groups you want to have access to this page.
- To just give rights to the page you have selected choose to Save. If you want to give rights to all subpages as well choose to Save and Push Down. Save and Push Down will wipe out existing permissions and should not be used if you have already given some rights to the pages.