Read the docs from MRTG :). Learn to use MRTG :).

Change "ADMINDIR"   in  the Makefile to where   you   want to  put the
executable and the tables.

Change "$SNMPGet", "$TableBase"  and "$Community" in GetSNMPLinesUP.pl
for your correct values.

See sample.cfg for a sample configuration entry of a machine with some
modems connected.

See ModemTable.dial-machine for the  corresponding variables to  check
in this sample.