Make edges of a picture tend to transparency

Np.... Here:

http://www.mardala.com/john/gradient.htm

It shows where to select gradient opacity.
What might be confusing you a bit is that the gradient would be a layer on top of the picture. If you select an area within the picture Like an olval or something, feather it, then select the inverse, the gradient will avoid the image and feather into it a bit.

Thank you very much.