I’m trying to amend my return so that my mom can claim me on her taxes. I’ve looked in turbo tax and cannot find where to click that I can be claimed as a dependent?

Click on My Info on the left side of the online program screen.  Edit your personal information.  On the screen labeled Let's check for some other situations then select Another taxpayer can claim me as a dependent on their tax return

By the way,  if your mom tries to efile and it rejects she will have to print and mail her return.  Once your ssn is in the IRS system she can’t efile it again.  

I am not sure by your question if you have filed a tax return and you are actually amending it or if you are trying to change it before you have filed it.  If you have already filed your tax return and are preparing an amendment you will have to wait until your return has been accepted.

Your parents may have to file their return by mailing it if you have already filed your tax return and you need to amend it.

If you are using TurboTax Desktop, after you enter your name in TurboTax the following screen asks "Do Any of these Apply to YOUR NAME?" And you will select "Another taxpayer can claim me on their tax return." and "Another Taxpayer will claim me in 2024." If you click on "Edit" after your name, you can review the screen and change this entry.

If you are using TurboTax Online you will do this, as DoninGA mentions above, by clicking on "My Info" on the left side of your TurboTax screen. You will see a screen that says "Let's check for some other situations" and you can select "Another Taxpayer can claim me as a dependent on their tax return"