Welcome to Android Central! The Play Store used to have an option to automatically add a homescreen shortcut for any newly installed app, but they took that option away. Now, if you use the Pixel Launcher, it's in the homescreen settings. Long-press any empty part of the homescreen, then tap the Settings button. On the Pixel Launcher, there's an "Add icon to Home screen" option. If you have a different launcher, go through the same process and see if that option is there as well.