once i make my finnal image, i have my canvas set to transparent, but when i save it as a jpeg, how do i keep the background transparent instead of having it white,black ect.

You can't keep it transparent. Picture viewers other than photoshop won't keep those layers. You have to give it a background. What are you trying to do?

make like a water mark for my high school videoproduction class. like to puton still photos and junk

I'm not familiar with photoshop because I use Fireworks but I'm sure they are pretty much the same. You'll have two different photos. Your first one will be the image your wanting to have watermarked. The second image will be the actual watermark image. Crop the water mark image with the transparent background and then paste it over the image and move it to where you want it and save. Does that help?

Save it as a PNG or GIF. Those formats will retain the transparency.

Download and use iwatermark.

Save the image as a .gif file instead.