How do I go back to correct an error when I am being told I am ready to file?

I incorrectly filled in the tax payments by quarter on Form 2210 & need to make the corrections, but when I logged back in to my return, I was at the filing stage & cannot get back to the actual return.  Also, I paid estimated taxes for the first time in 2018 and do not know where I indicate that and it doesn't seem to be figured into the amount of federal taxes I still owere.