You can review the IRS publication 969. https://www.irs.gov/publications/p969
Basically, you should contact the account custodian to withdraw any contribution in excess on the amount allowed in order to avoid a 6% penalty. You must be clear that you are requesting a return of excess contribution. Do not make a normal withdraw as that will not provide the desired result of lowering your contribution. You must withdraw the excess before the tax filing deadline (typically April 15). Do you have a specific question regarding this subject?
