using the materials can be a pain, but look on the forum there are a number of questions about this
e.g.
:: View topic - using pigms and igms within blendigo?
But in general terms you should look in the .igm file and find the material name, this name must be set to the same in blender.
I have not explored much into UV mapping but there is somethings about the UV names as well.
Oh : one thing that took me a little while was to figure this, download the material file, and in blendigo set the material to "External" and choose the file to use it. Observing the above naming schemes