Assuming the jailbreak worked and you have Cydia but you cant sync:
Open Cydia > Manage > Sources > Edit
Add source “http://cydia.hackulo.us”
for 3.0 and 3.0.1 go to
Section > Hackulo.us > “AppSync for OS3.0″ > Read info
for 3.1 go to
Section > Hackulo.us > “AppSync for OS3.1″ > Read info
Install.
Turn off your phone then turn it back on and Re-Sync.
MAKE SURE YOU ARE ON OS 3.0
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