Your question raises other 1. do you have any security, 2. Does the maker of the note have any means of paying it back, and 3. Are you willing to reduce the note to a judgement ( go to court)?
You can turn the note over to a collcetion agency and they will take about half of everything recovered plus costs off the top.
You can go to court yourself, ( not reccomended)
You can sit down and explain the facts of life to the debtor, that now is the time to start paying off the note, before the costs begin to pile up and communcation will be impossible.