I have imported an .obj file exported from my 3D software with the image of a face on it. Into Poser 11.

In my 3D software the plane is transparent and only the face shows.  

How can I make this happen in Poser 11?

the plane obj is white which I do not want. I want only the Face to show.

Thank you.      

IMHO, you need a transparency mask.

I'm told you can configure Material, Advanced, to use a PNG's Alpha channel as-is. I'm still learning that route.

Your guy's PNG does not have an Alpha channel 'mask' for his face, it's entirely white. So, gotta craft a stand-alone mask...

I pulled the pic into free, remarkably nimble Irfan View. Flood-filled the white surround to black with edit's 'paint' tools. Used 'image' tools to replace the face colours with white until only eyes and mouth remained. Back to 'paint' tools, brushed away the left-overs. Saved file under different name, to be sure, to be sure...

"I'm told you can configure Material, Advanced, to use a PNG's Alpha channel as-is. I'm still learning that route."

 Thank you for the answer to my question.

I understand what you did and I thank you for you time.

I think there might be something along that line in Poser 12. I don't think it's in 11.

The PrincipledBsdf node in P12 can access the alpha channel in PNG's.  But this node is not available in P11, you would need to use the conventional transparency map and a different node arrangement with Cycles to achieve the same effect.

In my PP_11.3, when you set a 'Diffuse' texture, the 'Image Map' whatsit that pops-up attached in 'Advanced' has several options for 'Image Mapped'. Default is 'Tile' but, IIRC, there's also 'None', Clamped' and 'Alpha'. Latter does not seem to work as-is, but I've not really explored...

Spent too much of yesterday wrangling a balky texture on ported 'PMX' model, as its 'sky island' 'owl' plinths showed black. Finally found I had to set that texture's pop-up's V-Scale to '-1' from 1.00 default...

Yes. Poser 2014 - export obj, import obj, use image map and transparency map on it and voila! every part that had been transparent is black now. Used the same material settings, changed primary and diffuse colors to white (in hope the object may become invisible ha-ha) - still the same.

PS - Ah, I exported it again to 3ds, imported and set the same material. Now there is transparency. I don't know whether it is a sufficient replacement.