Changing the ubuntu icon?

[newobo]

Okay Im brand new to ubuntu but I have been custimizing the panel for the windows users in my house. I was just wondering could I change the ubuntu icon for a personal touch. I have made a green ubuntu icon called start-here.png it is a 22x22 icon and I tried two guides to do it but no luck. Does anyone know how to change the icon???

I messed it up now it looks like this
http://img361.imageshack.us/img361/3676/screenshot1gf7.th.png (http://img361.imageshack.us/my.php?image=screenshot1gf7.png)

[newobo]

I want it to look like this http://img68.imageshack.us/img68/4245/screenshotso5.th.png (http://img68.imageshack.us/my.php?image=screenshotso5.png)

P.S. Sorry I for posting here didnt see the other folder.