How to change the application icon?

I dont mean the icon that appear in the title bar but i meam the icon 
that appear in the windows explorer.
first Open notepad.
2- Type: IDI_ICON1 ICON DISCARDABLE "icon.ico"
     Note: ”icon.ico is the name of the icon you want to use. ”
3- Save it as icon.rc
     Note: When saving, be sure that there is no .txt extention in the filename, it should be a .rc. You      can change the filename to whatever filename you want.
4-Open your project. The *.pro file.
5- Add this line : RC_FILE=icon.rc
     Note: “icon.rc is the name of the .rc you previously created”
6- Save.
7- Place your desired icon to the folder where your project (*.pro) was located.
8- Finally, build/rebuild your project.