Where can i change the earned income amout? the site said i could enter it to check to see if it would increase my refund and now i dont know where to redo it.

You may use your 2019 income for the Child Tax Credit if your 2019 earned income was morethan your 2020 earned income.  If your 2020  income was more than your 2019 income then you cannot use the 2019 income.

You can look back and use your 2019 income for the EIC credit instead of 2020. How to use the Lookback provision

https://ttlc.intuit.com/community/earned-income-credit/help/how-do-i-use-the-lookback-provision-to-maximize-my-earned-income-credit-or-additional-child-tax/00/2134907

The amount I entered is my combat pay.  I know it's not counted as earned income.  The site said I could still check to see if it would increase my refund, so I did check it.  Now I'm not seeing where to change it back.

For the EIC & CTC the combat pay can be considered earned income.   Complete the EIC section in the deductions & credits tab again to make the election again.  This time instead of continuing forward you need to back up to make the change in the election.