Do you have any friends that know wood working, a school that teaches wood working, or something along those lines?
It's not required, but you're going to get into using power tools pretty quickly when it comes to working with wood and it's probably a good idea to have someone teach you hands on how to use some of the most basic power tools. Such as drills, routers, saws, etc.
No sense in losing some fingers for a cabinet.
Putting casters on is pretty simple. Position and mark where the casters are to go. Note your drill hole locations. Drill a hole where the bolt is to run through and like Hitek explains, use the largest bolt that can fit in the caster hole without interfering with the caster. I would use washers on the opposite side of the bolt to spread stress across the wood.