To set a Member as a BOARD Moderator
Admin > Boards
Go to the Board you want them to modify
Click the Modify link
Scroll down, Look for Moderators
Type the name of the member whom you want to Moderate that board, or click the exclamation mark there and you can search for their name.
To set a Member as Administrator or Global Moderator
Go to the Members Profile > Account Settings
Change their "Primary Membergroup" to the appropriate membergroup.
If you want to Promote them to Administrator or Global Moderator privately (so it does not show that they are in their Profile or posts) click the Show Additional Groups link and choose the group there instead.