You just file an answer to the summons/complaint regarding the debt & answer truthfully. If you have a defense such as SOL has elapsed, not sure valid debt, etc., you would put that in your answer. The court clerk can help you with how to answer a summons but, of course, they cannot tell you what to put in your answer. They can't give you legal advice.

If the debt is valid & the SOL has not elapsed, the plaintiff's attorney can be contacted before going to court to see if a settlement can be reached - possibly for a lesser amount and/or payment plan.