It is quite simple after you get the hang of it. Here is a step by step way to make someone a Moderator.

Step 1...
Go into your admin center.

Step 2...
Click Edit Boards.


Step 3...
When there scroll down to the Board you would like the person to Moderate

Step 4...
Put the name of the person you would like to Moderate in the entry blank then click "Modify".

You now have a new Moderator.