-make sure you have the figure selected
-go to the material room
-right click on the node that says "Transparency" -->new node-->2D Textures-->Image Map
-on the loaded dialog click on "none" after Image_Source and browse to your transmap
-set transparency to 1.000, transparency falloff to 1.000 and hook transparency edge and falloff to the same map by clicking on the node and dragging it to your image map.

That's it :)