Customize Applescript app icon

I have created my AppleScript, tested it, saved it as an .app and it works.

Now, how do I set a custom icon for it?

I have done a bit of googling and tried a few different things but cannot get it to work. The app is mainly for me and maybe some people I know to make workflows easier so having a nice little icon makes a huge difference. Can anyone help with this please?

Solution

Basically you need an .icns icon file.
Open your application with right-click > Show Package Contents
Navigate to Contents > Resources
Delete applet.icns
Drag the custom icon file into the Resources folder
Rename the icon file in Resources to applet.icns
To update the icon appearance open and re-save the applet in Script Editor.