How to Install Cydia
Cydia is an application created by Jay Freeman available for the iPhone operating system. The application serves as a package management system and allows users to browse and download applications useable on a jailbroken iPhone, iPad or iPod Touch. Most applications on Cydia are free and 3rd-party -- not from Apple's iTunes store. The Cydia store also offers several applications for sale.
Jailbreak your phone using a jailbreak tool. Examples include PwnageTool, Spirit Jailbreak, redsn0w or limera1n. Go to the tool's website and follow instructions for your operating system. Some of these tools include Cydia as an attachment, including blackra1n, limera1n and greenpois0n, among others. Other tools require you to retrieve and install Cydia yourself using an Internet connection.
Click on "Install Cydia," or select "Cydia" on any options list that may appear before running your jailbreak software. This ensures that the tool will come with the Cydia installer attached. Agree to the tool's user agreement. Once the jailbreak is complete, Cydia appears on your homescreen. Proceed to opening and updating Cydia.
Connect your iPhone to the internet if your tool doesn't automatically install Cydia,as with BlackRa1n, for instance, open the tool application to install Cydia. Look for a blank application on your iPhone after the jailbreak. It may also be called "loader" depending on the tool you use. Tap and open the application.
Tap "Cydia" once your tool application or the loader application opens. Select "Install Cydia". Wait for Cydia to install completely. If the application asks you to remove it once Cydia has installed. Tap "cancel" and quit the application. Check for Cydia on the homescreen.
Open the Cydia application on your phone. It will "initialize filesystem" if this is the first time opening the application. It may take several minutes. Cydia will close after this completes. Re-Open Cydia at this time.
Select the appropriate user category for Cydia. Different packages are viewable to you depending on the category you choose. Most users should choose "user" to browse and download common applications, unless you want to use the hacker or developer categories for more involved use.
Update the Cydia database when prompted with a "downloading packages" message, then reload its data. Allow the download to complete.
Choose "Complete Upgrade" when prompted to upgrade the package. Click "Confirm" to finalize the upgrade.
Close Cydia after the upgrade completes. Cydia is now ready for you to browse and install applications from its database.