Unzip it and open META-INF/com/google/android/updater-script with notepad++ or some other text editor. It should be pretty self-explanatory but you can try to google manuals for edify scripting. After you have edited it to your liking zip it again and just flash it. If you want to have it signed for some reason, you need to download signapk.jar from somewhere and proper keys.
I know this isn't exactly a guide for you but should get you going in the right direction.
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