The power plant is supposed to be placed on the beach or similar shoreline, and one of the criteria is that it's easy to carry with you before and after use. Hence the use of detachable bottles as ballast tanks, that can be filled before the tide starts coming in, and emptied out when the tide is on it's way out again. (to be moved back further out on the beach at low tide.)
There are no step by step, since this is a sharing of idea, not instructions on how to make it.
The higher row of tanks/bottles can be partially filled with water to work as a ballast. When the tide comes high enough the water will lift up the whole installation and push it further in.
There are still a lot of improvement to be done to this, as a second section behind the present installation to make it all more stable.
Please feel free to give comments, and please have a look at Kiteman's link since he is the one who started it all...