If you are referring to the Arizona School Tax Credit, then read the following:

Go through the Arizona state interview until you encounter the screen entitled "Schools Tax Credits". Check the box next to "I donated to an Arizona private school by April 17, 2020."

This will give you two more screens as you continue on which you can enter the organization's name, address, and the amount you contributed.

[Edited 3/23/2020 4"09 pm CDT - updated interview steps]