Navigate to the pages you want to restrict access to.
From the toolbar, select Options > Restrict access.
Verify your page is configured as Semi-public.
In the User or group type the group's name (the field may auto-populate).
Select the group role depending on the tasks the group is allowed to perform on the page.
Click Add to list.
If restricting a whole section, click Apply restriction settings to sub-pages and choose the appropriate option.
Click Save permission settings.
New sub-pages automatically inherit the restrictions of their parent pages. You will not need to individually set restrictions for every new article you create under a restricted page.