Installing APKs (Android application packages) on a Chromebook can expand the range of apps you can use. First, make sure your Chromebook supports Android apps by enabling the Google Play Store in the settings. Once enabled, you need to allow installations from unknown sources by navigating to Settings > Apps > Google Play Store > Manage Android preferences > Security, and then enabling "Unknown Sources." Next, download the desired APK file using the Chrome browser. Open the Files app, locate the downloaded APK, and click on it to begin the installation. Follow the on-screen show instructions to complete the process, and the app will be installed on your Chromebook.