Obviously download Flash first. Whether you pay for it or not, and how you go about not paying for it is up to you.
After that do some googling and learn about how the timeline works and stuff, nothing code-related but just a basic understanding of the tools and the interface.
then head over to
http://www.flashgametuts.com/ where a guy very helpfully creates a bunch of games and walks you through all the code, explaining what each line is for etc.
Hope this helps at least a little.