They sell a coupling that simply screws into both lens. Just have to match up the diameters. In my case it's 52mm. Very cheap. Use the longer macro lens on camera as normal. Put the coupling on the end, screw the reversed 50mm unto it. On the 50mm make sure you have the aperture wide open at 1.8 so that light can get in. You do that through the aperture ring. Takes some getting used to, but it's alot of fun. Hope that helps, anymore questions feel free to ask.