car reads "oil level system faulty"

I bought an oil level switch but don't know how to fix it or where anything is located. i tried looking up videos or something but nothing seems to come up. my car oil light have been on since i got it (July 2014) i got an oil change and still didn't work so i ask my father (past owner) and he said the mechanic broke the oil switch and never fixed it..... Car readings says " PSI ---------" and sometime 0. any ideas if its something else?
p.s. have not put oil pressure switch on, NEED HELP.