Open Finder
Go to the Applications folder
Drag the app to the Trash
Empty the Trash
If the app has an uninstaller, open it and follow the prompts
If the app is from the App Store, open Launchpad
Click and hold the app icon until it jiggles
Click the X if it appears
Confirm deletion
To remove leftover files, check these folders:
~/Library/Application Support
~/Library/Preferences
~/Library/Caches
~/Library/Containers
Restart your Mac if needed