After you've parked, open the app and tap on the blue dot that shows your location. A window will pop up that gives you the option to "Set as parking location." That's it. Easy!
Actually, it gets even easier, because the app uses the Google Street feature to show a photo of where your care is, when you tap on the icon.
But there are other features. A bar will show up at the bottom of the Google Maps screen called "Parking Location." If you tap on it, other options open up to you -- like leaving notes, such as the precise location of your car in a parking garage. And the ability to Share your location with someone who you might want to meet at your car.
It's available for both Android and iOS.