#2 Jul 14, 2017 00:19
Did you installed the demo data on your site? There is a default "About blog X" page already created for each collection.
If you didn't install demo data for collections, you must know that the "About this site" page is a post of the type "Standalone page" that belongs to the main collection. So if you want an "About" page for each one of your collections, then you just need to create a new page of this type on each one of them (see screenshot below), by following the regular process of posts creation.
I guess I don't fully understand question number 2. What do mean about hiding the main collection? what link do you refer to?
As I see, maybe you just would like to hide the Site skin (the black bar at the header and the footer common to all the collections). You can find the configuration parameter that controls this feature at Site > Site Settings (http://b2evolution.net/man/global-site-settings).