However you want to, as long as it's sufficiently random. You can make a bunch of proxies and shuffle them, use Apprentice, or whatever. Someone (I forget who--again) here even made an Excel sheet that has everything set up for you and all you have to do is paste your decklist...
P.S: I don't mean to double post, but you do know that the minimum library size is 40 cards? Do you really want to use a 60-card deck or is that just a typo?