How do I find line 23210 for CERB repayment? I filled in a T4E lines 26 and 30 for tax year 2022. Is that all I need to do?

Yes, you just need to fill in the T4E and the information will automatically go to line 23210. 

You can see this line by looking at the detailed summary of my return in the online edition of TurboTax. This FAQ shows you how to get there: https://turbotax.community.intuit.ca/questions/1189958