OK. got that sorted out. Now I made the displacement map (which is really a 'transparent map' isn't it?) added it and then 'upped' the value to 1 as I couldn't see any difference. This is what I got.. which still doesn't look any different. I have a tut. on making displacement maps and second skins by SVDL, but it's been done on a PC and there are subtle differences and it's just not working with my mac. 

What do you suggest now?

Larger one has the displacement map.