The steps to renaming a file...

Right click on the file,
then click on 'rename'.
The name of the file will then
be highlighted in blue, which you just type over.
There you have it...
a renamed file!!!

To change the extension of a file...

You may need to change the .html extension to .txt at times while you are editing, or back from .txt to .html. If you can see the file extensions on your files in the documents folder, just rename it with a .txt or .html extension like you were just shown. If the extensions aren't there, use the following steps:

To do this, open up your document folder
then go to the top and click on 'view'. Then click on 'folder options'
Along the top, you will see some on 'view'.
Uncheck 'hide file extensions for known file types'. Click ok, and you're done.

This then causes the file extensions to show, and if you need to edit your html file but can't open up the source, change the .html to .txt and it will then open up in notepad. You then change it from .txt to .html when you've finished. Simple, huh!