To moisten the bedding, simply add the bedding material to a clean bucket or tub and start pouring water in. Mix it into the bedding well, adding a little at a time. You want your bedding material to feel like a wrung-out sponge. A couple of drops should be released from the bedding if you squeeze a handful of it; if more water drips out, add a bit more dry bedding to get the moisture levels right. Once the bedding is right, dump it into the bin, fluffing it up a bit. You want your worms to be able to wriggle easily through the bedding. Break up any large clumps of bedding.
If it is at all possible, add a shovelful of garden soil or finished compost to your bedding material. It will provide grit for the worms, as well as introduce microorganisms that will help the contents of your worm bin break down faster.
One final tip: it is a very good idea to wear gloves for this step, unless you like the look of ink-stained fingernails.