Wordfast Pro supports machine translation with Google Translate, MS Translate & WorldLingo.
Yes, these three, and no others.
Does anyone know whether MyMemory can be used with WF Pro and if so what is the procedure for configuring it?
You can't. In practice, MyMemory is Google Translate for free, but without the reliability of the "real thing". Why not get the real thing, for a mere 2-3 euros per month?