If you would like to restore your device for jailbreaking, now is the last chance for a while (probably until 9.0.1 or so).  It is not difficult as long as Apple is still signing the earlier version.  Simply visit https://ipsw.me/ and download the iOS version you wish to install (for us it is 8.4 for your device model).  Once this file is downloaded, fire up iTunes select the summary screen for your device, hold option (or alt if you are on windows) and click restore.  This will bring up an open dialogue and simply feed it the file you downloaded in the previous step.  You will need to temporarily turn off Find My iPhone before you will be allowed to restore.  Restoring creates a cleaner foundation for the jailbreak.  It is not always required, but i highly recommend it.  Soon, we will not be able to restore without loosing jailbreak.  We want to ensure that our devices are functioning fully.  That is why we jailbreak!

check status of apple signing:
http://api.ineal.me/tss/status

TaiG now has a mac version. Download jailbreak here:
http://www.taig.com/en/