Refer here, http://www.idownloadblog.com/2014/10/22/how-to-install-cydia-on-ios-8-video/, but if you got problem. try this method:
Download
proj_1.1.12_iphoneos-arm.deb
cydia_1.1.13_iphoneos-arm.deb
open pangu at phone. install openSSH
install WinSCP
Ensure
that your PC/Mac and iOS device are on the same Wi-Fi network. Get the
IP address of your device from Settings > Wi-Fi and tap the “i”
button against the network you’re connected to. Note down the series of
numbers labelled IP Address.
Now open WinSCP and SSH into your
device, with the address as the IP address you got from the earlier
step, and the username as ‘root’ and password as ‘alpine’ (both without
quotes).
1.Go to /var/root/Media/
2.Create folder "Cydia"
3.Create Folder "AutoInstall" and copy the two .deb files in there, right click, properties, tick all permission.
4.start an SSH command line session, type "reboot"
