The extention of .ahf doesn't play in your default media player ie Microsoft Media Player... so you need to convert it to an AVI file, .avi. With the film viewer you want to hit "Save as Avi" You will have the option of what screen size and frame rate you want to save it as... also you will get a little box with your choice of Codec's you can save it as..Uncompressed, mpeg-4 and etc... From what alf was saying Mpeg-4 seems to be your best bet... good quality and doesn't take up to much memory.
After that you want to import it to Microsoft Movie Player... There are other editors out there, but just starting it would be a safe bet just to use that because it is free. Sony makes one that is a little bit of an upgrade of that, Sony Screenblast, but there are others like Ulead... The high end editors are like Adobe Premeire and Sony Vegas will run up into the 800 to 900 dollar range to purchase. You do get better options and editing quality but it takes a little time to understand them.
You and also import MP3 files into movie maker for music to add to your film...
Just don't rush it so you can get it out.... take your time till you think that the film is perfect to your standards... You want the film to flow... or even writing a little script before you start doesn't hurt....
After that you need to find a hosting site to upload to show people, depending on the file size there are some out there... I use Neptune,
http://www.neptune.com they seem to be okay... not a lot of hassle...
Hope that helps a little, if you have anymore questions just ask and I will be happy to answer them... as I am still learning myself how to do this....
Good Luck