What do I call the host file?

You can call it anything you like and put it anywhere. It's passed to PVM (the console or pvmd) as a command line parameter. For example:

    ig 3; cat > H
    thud
    honk
    ^D

    ig 4; pvm H
    pvm> conf
    3 hosts, 2 data formats
                        HOST     DTID     ARCH   SPEED
                          ig    40000    ALPHA    1000
                        thud    80000     SUN4    1000
                        honk    c0000    ALPHA    1000
    pvm> halt
    libpvm [t40001]: mxfer() EOF on pvmd sock

    ig 5;