Carry out the following steps:
In the same dialog (refer the preceding screenshot), change Currently Viewing to Sub-Page Permissions to get a list with groups and page types, as shown in the following screenshot:
Switch the value in the drop-down at Set to Manually.
Select the page types you want your Editors to be able to add as subpages.
Click on Save to apply the new settings.
If you have a person who's only responsible for managing press releases, they only need one page type. By using the advanced permission mode, you can make sure that they don't see and care about the other pages types.
This is useful if your website gets bigger and has lots of page types. However, keep in mind that it might help your end users, but also increases the effort necessary to manage the website.