This is kind of a tricky question because nameofpage.webs.com/index.htm IS nameofpage.webs.com — it just doesn't show the index part. You'd have to name your file index.htm or index.html (I would recommend .html over .htm), and then you should be able to type in nameofpage.webs.com and have it take you to nameofpage.webs.com/index.htm without actually showing the /index.htm in the URL bar.
Basically, if I upload a file to my webserver that is index.html and then type in www.mysite.com, it will automatically show www.mysite.com/index.html. The index is the home page.