Each of the candle holders is a bolt that is going to sit in a hole cut out of the base. To cut these holes you're going to need to find yourself a set of drill bits or routers and a power drill is definitely recommended. Each bolt is 3/8" and therefore you'll probably use a 5/8" cutting piece to make the hole for the top of the bolt.
Clamp down the wood base and begin drilling out each of the holes. Make sure you don't drill too deep. I put a piece of tape on the bit I was using so I could clearly see how deep I was going. Once I was done I passed the base on to my girlfriend to put the candle holders in place.