There’s even an easy way to delete apps you’ve purchased from the Mac App Store these days, aside from the tried and true “drag app icon to trash” method we’ve all grown to know and love since OS X debuted oh so many years ago.
To safely delete apps you’ve downloaded from the Mac App Store, simply launch Launchpad, the new Apps layout screen that looks a lot like the iOS home screen, with each app getting its own icon.
Click on any app in the Launchpad screen, and hold the mouse button down. The apps will all start to wiggle. The ones you’ve downloaded from the Mac App Store will show an iOS-like X in the upper left corner of the app icon. Click this X to delete the app, from the Launchpad and from your Mac.
Apps that don’t show the X will require you to go into the Applications folder on your Mac and drag them to the Trash to delete. Or, you can click on their icon in the Applications folder, and hit Command-Delete to send them to the Trash. Don’t forget to empty the Trash once you’ve done that, as well.
Source: Apple Support