I'm trying to monitor a normal C program in Monit, but I don't know how to run the program, what configuration should be set in the control file of Monit.
You need to get the PID of the program to be able to monitor it with Monit. Some programs allow commandline arguments to give the location of a file that they are to write their PID to. Otherwise, you can try starting the program from a wrapper script that writes the PID to a known location, e.g. /usr/bin/myprogram & && jobs -p > /var/run/myprogram.pid in bash.