[Request] Alpha Channel

i wanna make a custom holo sight, i tested it without alpha channel, with alpha channel, but my alpha channel is all over white...

how to get the RGB sight into the alpha channel? cause i cant jst repaint it. is it because i changed it to PNG to edit it with Paint and GIMP, since i cant download the dds plug in for GIMP

uhm, if you convert it to .png, exactly how do you plan on getting it back? And the alpha channel is supposed to be all white. No color belongs on it at all.