Adding Google Play support to Anbox is a multi-step process that requires installing the right tools and playing around with some configuration files. Luckily, there are plenty of helpful guides out there that can walk you through the process.
To start, you'll need to install the Anbox toolbox, which you can get from GitHub. Next, you'll need to grab a copy of the Google Play Store APK. You can find plenty of these online, but make sure you get a version that's compatible with your Anbox setup.
Once you have both of those files, you'll need to modify the Anbox configuration to point to the Google Play Store APK. This is done by editing the configuration file located at ~/.config/anbox/container_manager.cfg.
In the [container] section of the file, add a newline with the following:
Save the file and close it.
The last step is to launch the Anbox toolbox and click the "Launch" button. This will start the Anbox session and allow you to access the Google Play Store.
Keep in mind that this is still an experimental feature, so you may encounter some bugs. But it's a great way to get access to Android apps on your Linux desktop.