1)PER FACES SELECTION MAPPING
2)USING THE EDITUV TOOL
 
 
 

1)PER FACES SELECTION MAPPING

Having the model ready(tex set,geometry finished) get into Face sub-element mode, select faces for each side of the model.You can select left-right,top-bottom,front-back faces.
*Check the Ignore Backfacing if you only need one side, i.e. front instead of front-back.
Use rectangle or contour pick mode and try selecting only the faces you need.Another way is to select the whole mesh and then remove unwanted faces from selection.For adding hold the Ctrl key while picking, for removing the Shift key.The selection should look like this:
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Now, even if it's not necessary(objects are uv mapped when created) go to UVmapping modifier and apply a planar mapping so that the UV points are setup for further processing.
*If the selection's size is not big enough and you don't want to scale it in EditUV, scale the gizmo(the yellow graph).

Exit modifier and press the EditUV button.
NOTE: If you can't see the UV points/faces it's because UVmapping sets negative values sometimes(this needs fixing).Pan the view to find them,select and center them to image.This can be avoided if while applying the planar mapping you flip vertical and/or horizontal.From now on you select,move-rotate-scale to fit the UV faces to the image's correct place.It's a time-consuming operation so for next versions EditUV will have more operations to make things easier.

For each side(s) you must go through these steps.