You have to ways to get page access configuration
1) Administration -> Access -> Resourse Permissions -> Pages -> Lookup page -> Press Key Icon
2) Manage pages -> Lookup page -> Press Key Icon
You'll see grid with access levels. Choose use User access level and press edit. After that you can lookup your users/grous and assign it to page.
Allow inheritance means that your page would inherit parent page access properties. Allow propagation means that your page would propagate its access properties to children pages.
And do not forget press button Allpy before button Done.