new to android: changing icons

[johnny quest]

Hey gang, I started to use better cut and its going great but I loaded from the market "handcent sms" but I want to change the icon. How do I change the icon?
I connected my phone to my computer and dragged the file and changed it to a Zip, I unzipped it and changed the icon but how do I change the file back to a APK file?

 

[takeshi]

Seems like it would be opposite of how you made it a zip. I.e. rename it from zip to apk, right?