If you're building a retaining wall, staggering the seams does more than looks good...it's a requirement to make the thing structurally stable. Otherwise, you're making a bunch of small, unconnected, unreinforced walls that will all fall over, or get kicked over, in a short amount of time.
2# hammer and cold chisel will split them, as will a guillotine style splitter - it sounds like this is something new for you, so buying the guillotine style might be too much for you (between $500 and $1,000), but they can be rented. If it's not a big project and you don't plan on doing much of this kind of work, $15 will get you the hammer and chisel. Just score all the way around then split it the long way.
Check with your supplier and they will likely have brochures, videos and such to help you with the installation. Make sure you have your base prep right. If you aren't sure how to go about that, run a search here and you'll find all you need.