Step 1: Download it and place it in your SD CARD
Step 2: Restart your Phone, it will now prompt your for a update, Click on update!
Step 3: If step 2 didnt work, switch off your phone
Step 4: Press Volume Down (Press this first) and Power Button for 3 to 5 seconds
Step 5: Navigate to Recovery..
Step 6: Select update from SDCARD option
Step 7: Select .Zip which you downloaded and place in your phone
Step 8: Sit back and relax it takes 5 to 10 mins to update
Step 9: Restart your phone.
It's kinda tricky to get it to work, I have the same issue here. Keep trying, if all else fails, wait for someone else to say something as I am not sure how to proceed any further. Sorry mate.