iPhone 4 damaged Home Button Repair manual

http://guide-images.ifixit.net/igi/J1G6bkQbpl1cIGry.standard
You can use this guide to replace a damaged home button to regain use of your iPhone 4.
Just follow on the instruction  on the link below on how to do it properly without damaging your iphone.

Guide on how to repair and replace iPhone 4 damaged Home Button