you'll need to download the itch.io app for your android phone, once install you'll neeed to login to your account once your login and can access the game (i'm assuming you either are following the author and the game/novel in your collections or have bought it either way once you tap on the game you scroll down to the download option tap the one for Android APK file and then wait while it downloads once it downloads it should give you a prompt to open the folder where it has downloaded. tap the file and your phone should just know how to install it.