To change the system icons: the Finder, the Trash, the system folders (Documents, Movies, Music, … you need the help of software.
I will first of all explain CandyBar. This software is the best choice, a real Swiss army knife of Mac enthusiast customization, but it is not free. There is also LiteIcon, that is free, but less comprehensive and can not manage your icons.
Remember that a presentation of different software for customization on the Mac goes in the Apps section, I am here only to explain changing system icons.
Candybar looks like iTunes. In the left column you can create folders, and collections of icons. At the top of the column, you can change several things. the first (the one we want) is for the System icons, the second is for the application icons, the dock for the third and volumes (Installed Disks) is the fourth.
The right part is divided into two parts. Above we see the icons you can replace and below we see the icons in the folder or collection of icons selected.
You just have to move your icons you put in your collection in candybar on to the elements of the system that you want to change the icons for.
Next is the free solution that allows you to change System Icons, LiteIcon.
LiteIcon allows you to simply and only change all the system icons. Just drag the icon in your format, Icon. Icns or. Png on the icon you want to replace to implement the changes.
For some icons you need to relaunch the Finder, a button on the top right allows you to do so.