Click the "Download for Android" button on your phone to start the download. If the button doesn't work you can go to your Phone's "Settings" and search for "Install apps from external sources". Find the browser application you're using and turn it "on".

If you're not asked to install the app automatically you should find the install kit in your downloads folder. Please click it to start the installation.

On Android 8 or higher you might get a dialog saying "Chrome, For your security, your phone is not allowed to install unknown apps from this source". Click the Settings button of that dialog and toggle "Allow from this source".

The app should be available in the Google Play Store as usual the next time you want to update it.