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

Step 1...
Choose the member you would like to make a Global Moderator.

Step 2...
Click to view their Profile.

Step 3...
When there click "Modify"


Step 4...
Go to the bottom of the page where it says "Position".

Next to it it should have a drop down bar. Click the arow and it should drop down and say Administrator and Global Moderator. Choose Global Moderator, and there you go, you now have a new Global Moderator. You must now click Change Profile for it to take affect.