Actually 'Paste' is Apple-V
To complete the process:
Click on the Icon you want to use, Then Get Info (Apple-I), then click on the icon image in the get info box, then Apple-C.
Now Get Info for the icon you want to replace, Select the icon image in get info, and Apple-V
The Icon does not always change immediately, you may need to logout, then log in, Some folders have icons that do not change readily, such as the standard folders in your Home Folder (Documents, Pictures, Music, Movies, (etc), Any folder that YOU have added should always accept a different icon.... Good Luck!