What should I do if I did not know I needed a 1099-C form to file my taxes back in 2016 and just now received a tax bill from the IRS?

I did not know that discharged debt on an equity line of credit was supposed to be reported as income. I never knew what a 1099-C form is and that I should have received one in the mail but never did. I recently received a tax bill from the IRS stating that I owe the difference on tax not paid on unreported income. How do I deal with this now since I cannot pay the amount owed by 02/01/2018?