start pvm:
export PVM_ARCH=LINUX
you should put this line to the ~/.bashrc file too (see: usage.txt)
pvm <command>
commands:
ps - process list
halt - exit
exit - exit; pvmd continuous

the pvm creates files in the /tmp directory with .$UID postfix
if the pvm doesn't start, you should delete these files and try again
the messages of the programs started from pvm are in the /tmp/pvml.$UID or in the /tmp/pvm.$UID/log  

required for compiling:
/usr/lib/pvm3/include/pvm3.h
/usr/lib/pvm3/lib/LINUX/libpvm3.a 

(or /usr/share/pvm3 - depends on the installation..)

option for gcc (or in a Makefile) 
-I/usr/lib/pvm3/include

cc something.c -o something /usr/lib/pvm3/lib/LINUX/libpvm3.a

pvm methods (see man)
int pvm_mytid()
the tid of the process -- you should start the program with this call
int pvm_parent()
the tid of the parent process or PvmNoParent (negative integer)

int pvm_spawn( char *task, char **argv, int flag,
        char *where, int ntask, int *tids )
starts the file in the task parameter ntask times
the new process ids will be in the tids array (or error codes)
return value: number of tasks started

int pvm_initsend(PvmDataDefault)
initialize the buffer 

int pvm_pkint(int* p, int cnt, int stride)
manpage: pvm_pack
puts an integer or integers to the buffer. similar methods for other types.
p: address of the int; cnt - pieces  stride: hanyasaval (in a simple case: 1)
return value: error(<0)

int pvm_send(int tid, int tag)
send message
tid: destination process; tag: label

int pvm_recv(int tid, int tag)
receive message
tid: from which process (-1: from every process)
tag: which label (-1: every tag)
return: buffer id or error (<0)

int pvm_upkint(int *p, int cnt, int stride)
manpage: pvm_unpack
parameters are same as at pvm_pkint