I am working on a police car and I have applied Architectural materials (gloss paint) to it.
On the doors, I created a logo in photoshop (.psd with transparent background, and also a .tiff with alpha channel).
I cannot successfully figure out how to get this decal on the painted door.
Can someone walk me through the steps? I can send the model and decal to someone if that will help.

WINXP SP2 32bit 4gb RAM - 3ds Max 2009

There are a few ways to go about this.  In your material, you can set the Diffuse to use a Composite Map.  Or you could create a new material for the decal, and nest it and your paint material into a Blend material with the TIF’s Alpha as the Mix map.

Check the Help file in Max for more info, and let us know if you run into any problems.

3DS Max Design 2011 64-bit - Advantage Pack
Dell Precision T5500, Dual Six Core Xeon X5650 @ 2.67GHz, nVidia Quadro 5000, 24 GB RAM, Win 7 Enterprise 64-bit
Minneapolis, MN, USA