The next position you have is bottom. You start out in the bottom position if you pick it at the end of the three periods or if you are taken down. At the end of the period the ref tosses the coin to see who picks first. When you are on bottom you get set then your opponent gets on top. As soon as your opponent gets set the ref blows the whistle to start the second period. 

Your goal on bottom is to escape or reverse your opponent. The goal on top is to hold your opponent down and get near fall (back) points or pin your opponent. To escape from the bottom position you can do many things. There are many different types of stand-ups, my favorite to use is the baby stand then knee slide out and get 1 point. 

You can also reverse your opponent to where you become in control and are on top. There are many reverses and my favorite to use is the Peterson.

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When you hit the Peterson you get 2 points for the reversal and then usually 2 or 3 points for near fall points. So it basically becomes a 5 point move or you can even pin them from there.

I usually do those moves or I just get into a scramble and reverse the kid or escape that way. When you are in the bottom position it is usually the easiest to score from and take the lead in the match!