When you "walk through" something, you talk about it step-by-step. In the example above, the speaker says that his coworker is going to walk everyone through a new home page. That means that he's going to show them each new feature of the site. Some other examples of "walking through" something include:

• When you're preparing for a wedding, you usually walk everyone through what to do during the ceremony.
• You should walk your children through what to do in case of an emergency like a fire.