I need permission to use section code 174 and I need to add child tax credit from august to october missing payment.

Are you certain that you mean IRC § 174?  That has to do with research and experimental expenditures, and isn’t typically covered on an individual tax return.  See 26 US Code § 174 - Research and experimental expenditures.  Please provide more information.

To enter your advance Child Tax Credits, if that’s what you’re referring to, please see the TurboTax Help article How do I enter my advance Child Tax Credit payments in TurboTax? for guidance.  If this isn’t what you’re asking, please provide more detailed information.

To find the amount of advance Child Tax Credit payments you (and your spouse) received in 2021, please see the IRS’ Letter 6419, 2021 advance CTC, to find the total amount of advance payments you received in 2021. 

You can also check the amount of your payments by using the CTC Update Portal available on the IRS website.

If you’re saying you need to amend your return to include these advance payments, see the TurboTax Help article How to amend (change or correct) a return you already filed for instruction on how to amend your previously-filed tax return.