If you go to the download links, the instructions are posted below it. But here:
Instruction for TrueStory.rpy:
PC/WIndows/Linux
Move/Paste the TrueStory.rpy into the 'game' folder, next to the .rpa files.
MAC:
Mac: Right click the MytimewithyouCh8.app -> Click "Show Package Contents" -> Move/Paste TrueStory.rpy into they "Contents/Resources/autorun/game" folder
Android:
file manager>android>data>com.adroid.mtwy>files>create 'game' folder if none then paste/move the TrueStory.rpy into it.