follow these instructions if you tried using the full save but the extra scenes didn't work, and only got the saved games
you have to go to appdata/RenPy and delete the TheSagaraFamily folder (or change the folder name if you're nervous) and then copy the full save into your save game folder. You could also just delete or rename the RenPy folder.
I think the reason is, TheSagaraFamily folder in appdata/RenPy also contains the "persistence" file, and the game checks both "persistence" files, the one in appdata and the one in your game folder. And if the two files don't match, then it uses the most recent one (which is going to be your own file). So basically you need to get rid of the "persisitence" file in appdata, then you cna copy/paste the full save into your game folder.
This is true for all RenPy games. Like the recently remastered X-Change