To setup a payment plan with the IRS you just need to either go to your local IRS office or give the IRS a call and they should be able to work with you to setup payment arrangements to pay back the IRS taxes owed.
You might have to come up with a certain amount though before they'll setup a payment arrangement option but it's really easy to get the payment plan setup with the IRS if you just call them or stop by an IRS office.