To install this application you will need an android device. Then you will need send the "app-release.apk" in the root directory of the github repository to the device in some manner. To send the file to your device you could email it to yourself and view it on the device or use some file transfer/storage app such as Google Drive. Once the file is on the device, you should go to where it's stored (maybe using a file browser app) and try opening it. The install process will then automatically start. (To be able to install it make sure android setting for installing from other sources is enabled)