Hi,
Open your project, open project info dialog from menu Project->Project Info.
Check Attach icon checkbox to select icon for your app. The icon should has size of 16*16 and 32*32 pixel and with maximum 256 colour.
HTH
I am not the most powerful man in this world.
I am not the worst man in this world either.
I just as same as all of you.
I still need to learn from my mistakes...