I have a new install of Media Composer 3.5.  I want to cut some IMX 50 files from FCP, and have installed Avid Interplay Engine and Client, but have no idea where to go from here... These are not intuitive utilities.

What should I read & do?

Start with this attachment. I hope it helps you.

Did you get the training offered for Interplay?  Your re-seller/installer/system integrator should also be able to provide detailed level of help with workflow. 

Seconded. Interplay has a bit of a learning curve and you should take advantage of any technical training your facility can offer you.

I agree. Training on Avid Access and Avid Interplay for editors is a single one day session, but well worth it. Most facilities going to Interplay contract for this training. Understanding the Interplay folder structure is crucial.