Step 1: First you will need to have MobileTerminal installed on your iPhone so if you don’t already have it installed go and install it in Cydia (make sure you search for it Exactly as spelled with no spaces) ~ MobileTerminal ~
Step 2: You will also need Safari Download Plugin so if you don’t have it installed search and install it in Cydia
Step 3: Now on your iPhone open Safari and download the Cydia .deb file from here: Download
Step 4: Again open Safari and download this file: Download
Step 4: Now open Terminal and enter these commands below exactly as shown:
dpkg -i essential_0-1_iphoneos-arm.deb cydia_1.0.3366-1_iphoneos-arm.deb; respring
Note: Cydia file name must be same depends on the cydia package you are installing.
Step 5: Now it will install and respring.
Step 6: Congratulations, You now have Cydia installed, Enjoy!