How do I add another XML tag using Excel 2010?

Question

Quick example, my XML file:

<Customer>
    <Name>Jane</Name>
    <City>New York</City>
</Customer>

I want to add a new tag called Age:

<Customer>
    <Name>Jane</Name>
    <Age>29</Age>
    <City>New York</City>
</Customer>

How do I do this? I tried using right click, "Insert" but it doesn't work. Any help?