You can restrict access to certain categories of posts in the member level settings themselves.
To restrict other content, such as pages, edit the content you want and select the level (s) that can be accessed.
This option will be in the sidebar, both in Gutemberg and in the classic WordPress editor.
Don’t forget to save the content (page) before leaving.
For detailed information about this topic go to https://www.paidmembershipspro.com/documentation/content-controls/