[itsme]

Import the file as the first song.
Copy the song in MSP:
   long press (Android) or right click (Win10) it
   check the checkbox at the left
   click "Copy Song" in the menu
the song editor is opened and refers to the same file(s)
set the title
select the part of the file that you want to use for the new song:
   set "Page Order" on the "Files" tab
   crop unwanted parts
repeat if required

Any combination and sequence of pages from the file is possible, you can even repeat pages or change the page sequence

It works in the same way on Android and Win10, no matter if "Let MobileSheets Manage My Files" is set or not.
MSP takes care not to delete the file in case it is still used by another song.