How do you load an alpha from the lightbox interface into the brush alpha selector?

How do you load an alpha from the lightbox interface into the brush alpha selector?

Shift+double click on it.
If you are in edit mode, the alpha will be applied to the Smooth brush since that brush is activated with Shift. So the easiest is to first press T to exit Edit Mode, load your alpha, then press T to return to Edit mode.
Hi, may i ask why everytime i tried to load alpha from light box(with shift+double click /just double click) its always came up as image/texture slot instead in the alpha slot?
thanks!
I don’t know why it does that.
I just click the makealpha button in texture window and it kicks the alpha over to the alpha slot.

thank jcsizmadi, i tried that and it worked!
cheers