how do I sue for defamation of character?

I'm a nurse. My boss accused me of stealing narcotics and fired me even though I complied with drug test etc. And it was clear. I an the only nurse she drug tested. She fired me before she got the results. I cannot draw unemployment. This is a serious accusation for a nurse. My problem : She turned my name in to state. Now I can't get a job. If I tell a potential employer, I won't be hired. If I don't tell them, I can be fired for not disclosing this information. Managers check online before hiring. I feel my 19 year career in nursing is over. My reputation is ruined. No one will hire a nurse who was fired under suspicion of stealing narcotics. Or I could lose my license. I have proof of everything labs reports, separation notice, pharmacy prints, result of test. All this has dates, times, etc. What do you think?