You must set the environment variable PVM_ROOT to ${PREFIX}/pvm3 in your
startup files (.cshrc, .profile) on all machines in the cluster.  In 
addition, you may want to add the lines contained in 
${PREFIX}/pvm3/lib/cshrc.stub to the system .cshrc.

You can specify each host's run path in your pvmhosts file like so:
hostname ep=/usr/pkg/bin
This allows you to point different achitecture types to various sets of
shared or local binaries.  See pvmd(1) for more information.