Most of the explanation is now in a single PDF document explaining how to use Microsoft Word's Equation Editor.
Here are some videos that show specific functionality.
Historical Note: This document used to cover using MathType with Word. MathType got bought out and Word stopped including the watered down version with their software. My videos were made with Captivate, which used Flash and is no longer supported. The old pages are still available, but are mostly kept for historical purposes.