The first thing you need to do to remove both cranks from the bottom bracket.  Please refer to the "Crank Removal" procedure for doing that.

 The next thing you need to do is to apply the special bottom bracket tool to mesh with the teeth on the right side of the bottom bracket, the side that the chain ring crank is normally attached too.  This tool is shown in the photo at an angle but in reality would go in as straight as possible and as deep as possible in order to provide the maximum amount of removal strength.  In my case, due to debris buildup, I tapped the tool lightly with a hammer to lodge the debris loose and to ensure the tool was inserted to it's maximum depth.

Then, apply a wrench to the nut portion of the removal tool.  Alternately, if you have a 1/2" socket set, the end of this bracket tool will also accept a 1/2" socket rachet.  Contrary to normal removal, this bottom bracket has reverse threads and you rotate the wrech CW to loosen.

This is what my bottom bracket looks like.  It is a sealed unit and cannot be disassembled in any way without the use of special arbor presses and what not.  They cost about $25 to replace and it is unlikely you would ever need to replace it except for an upgrade perhaps.

If upgrading, note the stock dimensions of your bottom bracket and then replace with approximately the same. Two bracket dimensions are critical:  The distance from the end of one square spindle to the end of the other and the length of the bracket body.  In mine (this one) the spindle distance is ~114mm and the body is 68mm.

You can see by looking at the bracket threads, that they are opposite of normal threads in that they slant from the top CCW versus normal threads which would go CW.  This means that ccw turning tightens the bracket and cw loosens the bracket.  Another reverse thread situation besides the left pedal threads.

Reverse the above procedure to install the bottom bracket.  Note that the nut on the opposite side is a positioning adjustment  for the bottom bracket as well.  If you did not move or remove this nut, you should leave it where it is and tighten the bottom bracket against it.  If you did move it or remove it, when reinstalling this nut, ensure both sides of the bottom bracket are spaced evenly from the frame before the final tighten.

Now you can put the cranks back on.  Just slip the pedal cranks over their respective spindle knob and tighten down with a very healthy exertion on the tool tightening the bolt.  It is difficult to over tighten these crank bolts but it is real easy to not tighten them enough.  More is better.   Oh yeh, the crank with the chain sprocket, goes on the right side of the bike and the opposite crank should be mounted 180 degrees offset from the crank you are looking at. A simple common sense instruction but a dyslexic person might enjoy the extra instruction ;=)