A UV Map is a 2D representation of the 3D mesh of a Figure or Object.  Where two lines meet, on the map(a vertex), so will they on you figure's mesh( a figure in DIsplay > Wireframe mode.)  You need to find the UV Map, for the figure you want to use; or make one, with UV Mapper.  You also need to be familiar with Photoshop, or some other Image Editing Tool.  You could start be applying the UV Map, like any plain texture.  Now; pick a spot on the UV Map, add some color with your image editor, and save over the file you loaded into Poser(just make sure you have a copy around somewhere first)  Now, in Poser, click Render > Reload Textures(making sure Keep Textures Loaded is'nt checked. Now Poser will swap out the old UV, for the new one with the color.  This takes a second, but you can get around that; if you are willing to render the change.  Befoer you hit Reload Textures, make sure you are on the Render Panel, then hit render.  If you are not on the Render Panel, when you hit Reload Textures, Poser will pause for a moment to do the reloading; but if you are on the Render Panel, then it will do this reloading while it renders, and you wo'nt skip a beat!  Now continue to add sections of photographs(get used to Photoshop's Feather function) over your UV.  It's a good idea to use a picture of a nose, one of the eyes, the mouth etc.  then just cut out the impottant parts and composite.  Blurring, smudging, and te clone tool will also become your friend.  Another important tip would be to start, in photoshop, by making saving selections of your favorite areas.  I have a 100MB .PSD file that only has saved seelctions of certain V3 Material Zones, as they relate to the UV Map.  This saves time when you want to fix/edit your texture!