AppSync is a hack tweak patch to bypass Apple’s verify to install .ipa file for iPhone, iPad and iPod touch, if your device is not installed AppSync, you can only install genuine applications that you can install free apps.
Method 1 – Install AppSync on idevices iOS 4.3.3 via Cydia.
Making following actions, make sure your iPhone, iPod Touch or iPad can connect to the Internet via WiFi, and make sure your device is already jailbreak and installed Cydia.
Step 1: Open Cydia on your jailbroken iPhone, iPod Touch or iPad.
Step 2: Click on Manage button of Cydia interface, switch to the management interface
Step 3: Select the “Sources” into the source management interface and click the upper right corner of the “Edit” button to enter the source edit mode, and then click “Add ” button to add the new Cydia source.
Step 4: Tap on Edit button on the top-right corner and then tap on Add button on the top-left corner of Cydia.
Step 5: Enter http://cydia.hackulo.us as Cydia/APT URL and tap on Add Source button.
Step 6: Now wait while Cydia updates its sources database. Once done, tap on Return to Cydia button to view Hackulous repo.
Step 7: Tap on the Search tab at the bottom. Type AppSync in the search field and hit Search button.
Step 8: Select AppSync 4.0+ from the search results and tap on the Install button on the top-right.
Step 9: Now wait while Cydia installs AppSync on your iDevice. Once installed tap on Return to Cydia button and install Installous from Hackulous repo.
Download AppSync 4.3.3.deb file and migrate to var/root/Media/Cydia/AutoInstall and add it. This can be done by tools: iPhoneBrowser, iFile or iPhone Explorer. Reboot your device twice and start syncing your free apps on the jailbroken iOS 4.3.3 via iTunes 10.2.2
NOTE: If for some reason you are unable to add Hackulous repo to Cydia, you can still install AppSync for 4.0+ offline by using AppSync DEB file. Just download AppSync for 4.0+ DEB file from here and follow this guide to install it with or without SSH access.