If you are unhappy with an App Store purchase on your Mac, iPhone or iPad, you can request a refund from Apple. You can do so through the iTunes or Music app on your Mac, or through the Settings app on iOS. This works for music, video and books as well. You eventually end up at a special Apple site where you can request the refund. You can skip directly to this site if you know how. Apple doesn't always issue a refund and it helps to use this sparingly. You can also cancel subscriptions you no longer want.
If you are new to Mac you may not have had the chance to use the Mac App Store very much. The App Store is a great way to get all of your software since it is more secure, a trusted payment system, and easy to find apps you need. You can look at top charts, read reviews and search for apps. Any apps you purchase can be installed on all of your Macs.