Its not just a case of flashing these boxes, it doesn't work like that. You have to downgrade the original firmware first, solder some links on the mainboard and them use a program to set the box up to receive Enigma. It also depends on which chipset is on the box as to whether or not it can be done without having to de-solder and replace certain components.
There are guides around, unfortunately most of them are in Polish, so unless you are fluent in polish its going to difficult. There is a seller on eBay called Comet24UK who will sort the box out for you, hes done quite a few for me upto now and everytime i have been pleased with the results.
Leave it to somebody who knows what they are doing unless you are prepared to trash your box.
I have attached a guide for doing it, but its in polish, so you will have to figure it out for yourself, although in all honesty unless you are going to do a few of these you would be better just letting an expert do it for you.
Nano