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
- Select Live edit
- Select the Properties tab
- Select Permissions
- Select the groups you want to have access to this page
- Saving Options
- Save: To just give rights to the page you have selected
- Save and Push Down: If you want to give rights to all subpages as well
- Warning: Save and Push Down will wipe out existing permissions and should not be used if you have already given some rights to the pages.