You must set-up the SEPP with the plan administrator of the IRA.
Once that is accomplished your distributions from the plan will be reported on a Form 1099-R. On the form there should be a code of 2 in box 7 indicating Early distribution, exception applies (under age 59½) so that you will not be assessed the 10% early distribution penalty on your tax return.
For detailed information for a SEPP go to this IRS website - https://www.irs.gov/retirement-plans/substantially-equal-periodic-payments
