Open Excel, go to the Help menu, type in "macro" as a search object, and
browse through the results. Specifically look for "About macros", or
something similar.

Other places you might find of interest are:
http://www.mvps.org/dmcritchie/excel/excel.htm - look for "Getting
started with macros" almost halfway down the page.
http://www.exceltip.com/ - look for Microsoft Excel tips by categories.
www.google.com

There are many more sites that I can recommend, but you should be able
to make a good start with these basic articles.