Ok, simplest way to show how it's done;
I wanted to make a model of a railroad sign, first I made the model, just cubes of different sizes put together using the 'Combine' tool - You can easily UV map an object if it is one whole connected model, but I find it easier to combine it, as you won't have to UV map the joining, or bridging pieces.
I then made a texture using photos:
Then, I select the face I want to texture:
And click 'UV Mapping'
A newer, smaller window should appear, with just the faces you selected showing:
Select the face, click the line tool at the top. All lines of the face should now be selected, right-click and click 'Mark edges for cut'. Right-click again, and then select continue and then 'Projection Normal'.
This new window will appear:
Cross of that, then go to File>Import Image and find your texture picture, and click open.
Go to Window>outliner, and the outline window should appear. The image you imported, in my case 'ra.bmp' will be visible in the outliner.
Drag the image and drop it over 'Cube1_auv' and then select 'diffuse' Note: 'Cube1_auv' will the default name for the first object spawned in wings, you can rename them for ease of use, especially if you're making multi-mesh models.
Select the whole model using the body selction at the top, and click UV Mapping again; this should reapear, remember it?
Position and rotate it so it covers the part of the texture image you want it to show.
X off that and then it should appear like this:
And when it's finished it should look like this:
Note, you can do more than one face at a time, but remember to cut where you want the piece's edge to be.
Any questions? Post here, or PM me and I'll try and adress themEDIT: Added more info.