I filed single last year and this year head of household how do I enter my AGI ?

You use the AGI from your 2021 return.  Filing status doesn't matter.  You need your 2021 AGI to efile 2022. The AGI is on 2021 1040 line 11. If you filed a Joint return you use the same AGI for each spouse.

How to find the AGI.
https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/01/25947

If you didn't file 2021 or filed it later in the year or mailed it, then try entering 0 for the AGI. If that doesn't work you will have to print and mail your return.

Or request a transcript from the IRS
https://www.irs.gov/individuals/get-transcript

if you used Turbotax in 2021 and are in the same account as 2021 the AGI should have transferred when you started 2022. in any event it's on line 11 of the 2021 return.