You should note that if you have opened an app in a folder then you will not be able to return to the first home screen. In this case first you have to close the folder in order to return to the first home screen. We are expecting this bug will be fixed in the next version of this tweak. You can watch the video embedded below to see this tweak in action.
HomePage tweak is available in Cydia for free of cost. In order to install this tweak you will need to have a jailbroken iPhone. You can follow the step by step instructions posted here to jailbreak your iPhone on iOS 4.2.1 with Redsn0w.