Since HBO Max is not yet available in the Amazon Appstore, it must be sideloaded. Instructions for how to sideload the app can be found here, but you might be wondering how to update the app once you’ve already installed it. The process for updating is identical to sideloading. Simply open the Downloader app, enter the URL to the newer APK, download it, and install it. The new version will automatically update/replace the old version. You do not need to uninstall the existing version first. A new version 50.2.0.37 of HBO Max was just released and you can get it by entering bit.ly/firehbo (see update below) into the Downloader app. If you need more detailed instructions, follow this guide.