newbietelecom,
it depends on your switch model and version. if you have software older than r9.5 the only option available to you is to use serial port. on r9.5+ you can install (or use available) c-lan board and administer cdr collection through it. using serial port is different for csi, si and r models.
on the csi there is a processor cable with different connectors, one of them is 25-pin marked "dce" and is what you need. just connect it with straight (not null) modem cable to your pc serial port and run any terminal emulator program on this port -- if you have cdr administered on the switch you should be able to see cdr output.
on the si model there is a 25-pin connector marked "dce" on the back of processor cabinet.
on the r model there is no dedicated cdr port, you should use data module -- for example, 8400 or 7400 or z3a1/z3a2/z3a3 if you have tn553 circuit pack.