If you have the funds available for the credit repayment by April 18, 2017, you may want to consider filing and making the payment on your return - it will probably be the simplest solution.
If filing a return for the repayment is not a (good) option, it would be a good idea to contact the IRS directly to let them know how you plan to make the payment this year.
It can be almost impossible to get through using the national (800-829-1040) phone number. If possible, you may want to contact your local IRS office.
Please see this website (https://www.irs.gov/help-resources/contact-your-local-irs-office) to locate your local IRS office.
