How to change app icon?

[Cam493]

I've switched from uTorrent to Transmission, and my inner OCD is making me freak out over how small the icon is in comparison to other ones. I have a 512x512 icon I found. How do I replace it?

 

[simsaladimbamba]

Strange, since the icon of Transmission is 512 x 512 pixel in size.

How to set an icon for an application, file or folder & restore to the original icon​