A small number of simple Linux commands (i.e. these are all typed into the shell window) are required. Having written your source program, say in a file hellompi.c, you should compile it with the command
[mymachine]: mpicc -o hellompi hellompi.c
to create the executable hellompi. To run your successfully compiled program type
[mymachine]: mpirun --map-by socket:OVERSUBSCRIBE -np 8 ./hellompi
which creates 8 MPI processes each running a copy of the executable (in other words, this is SPMD style parallelism).
See Open MPI documentation for full documentation.