I'm not familiar with "Web Page Maker", so I have no idea what it will do. There is, presumably, a setting somewhere that will allow you to have index.html as your preferred home page filename. Their website has no online documentation or anything like that, so I cannot see whether or not it has that option.
Since you have a very simple, four-page website, you might want to consider learning how to code the pages by hand.
Simon Jessey | Keystone Websites
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