There are two reactors in this book, belt based and bot based. How to use? Just place as many reactors as you need in a row, supply with fuel and water (you need 3 pipes on each side of one reactor, so 6 per 1 blueprint) and you're good to go. Need more power? Just add another reactor to the row, extend the belt loop and pipe in some water!
NOTE: I did not make this blueprint, i had the bot based one in my blueprint library and used it for a very long time. Then recently i modified the bot based to be belt based for my no-bot playthrough. I was now searching for the source but i couldn't find it, so sorry about that, original creator. :-/
also sorry for my poor screenshotting skills