On the right side of the page, there are videos that show it. This site is great for so much. There are also spinning basics on You Tube with Abby Franquemont. I'm pretty sure it shows a bottom whorl.
ETA: Yes, here's the link. http://www.youtube.com/watch?v=drXid5cT0y8
If you search You tube with her name, you get all kinds of goodies.
My biggest thing was how to wind the yarn onto the spindle after I put twist in. Abby shows that too, how she winds it on her fingers in a figure 8 sort of move, or like making a butterfly of yarn.