Okay, here are some instructions : 1. Save your icon in the easiset folders you can remember e.g. /home/user/MyDocs/abc.png. 2. Locate the app you want to change e.g. /usr/share/applications/xyz.desktop. Some applications reside in /usr/share/applications/. 3. Open terminal, devel-su, password 4. Edit the app via nano, nano /usr/share/applications/xyz.desktop 5. You'll find "icon=zzz" 6. Change to "icon=/home/user/MyDocs/abc.png 7. Save it, done Hope this will help