All you have to do is tune normally, and once you've finished you'll find that the rest of the strings have gone out (as there's more tension, and the bridge moves). You then have to do this again. And again, and again, and again... it's a pain, but if you imagine the fool who convinced you buying a guitar with such a bridge having their knee caps being shot off it makes it a lot easier...
If you dont have perfect pitch and you try to use relative tunnig, don't bother it's impossible...
hope that's helped... :)