Step one: Once you have a jailbroken device, open Cydia.
Step two: Manage -> Sources -> Edit -> Add
Step three: Choose one of the following repo
Step four: You may get a Source Warning pop up warning you that the “repository has been reported by the community to be illegally redistributing copyrighted works”. To proceed, just click on Add Anyway.
That’s basically, installation of AppSync will begin, restart the SpringBoard and you’re done.