How can I claim the California Prison Inmate Labor Credit, Form 3507 using TurboTax?

If that form is available you can find it by using the search option or switching to the FORMS mode and searching there.

In Forms mode in the CD/Download version of TT, you can go to the California credits worksheet and enter your credit on the line for Code 162 - Prison Inmate Labor.  I don't know how you would do this in the online version of TT, since Forms mode isn't available.