Hello , I contributed into an rsp in 2023 and forgot to add this onto my 2023 tax return. What form do I use on turbotax so I can submit this electronically

After you file

This TurboTax FAQ tells you how do to enter RRSP contributions in TurboTax Online:

https://turbotax.community.intuit.ca/turbotax-support/en-ca/help-article/retirement-benefits/enter-r...

This FAQ has more information on changing your return using ReFile: https://turbotax.community.intuit.ca/community/tax-return-amendment/help/i-have-filed-my-tax-return-...