First after you get the proper flash animation programs which you can get of the internet, but watch out for viruses, trojans etc.. After that I would suggest reading the tutorials on how to use that specific flash program properly. Once you know what you can do you should just make a few very good picture/scenes, and just animate it from there. In fact it's much easier to just use the original flash picture/scene parts over and over again, but just animate the picture/ scenes differently each time. If you want to go full out on a flash it takes about two weeks worth to make a good flash. If you want to get more help I'd suggest going to the BBS(forums) then going two programing and making a topic on how to make flashes, but be careful the people on newgrounds can't always be trusted, Remember google is your friend <-- HINT

Start with movies, and if you get used to flash, look at AS tutorials.

Thats how I did it.