Ok you have SPRecovery, download the rom to your pc and rename it to update then plug in your phone and mount it to your pc and copy and paste the file to your SDCard, not in any folder. Then unmount your phone and power it off. Hold doown the X on your hard key board and power it up (keep holding X) when it comes up use your volume buttons to go down to wipe data or something like that (this will wipe all data from your phone and you will need to setup your gmail account again. then select install zip from sdcard (or something like that) then use you camera button to select it. New menu, select the 2nd option down allow install zip (or something like that) then select the 3rd option down.
Once done reboot and you should have NexBeast