Hi Maureen,

I don't believe it is currently possibly to add the Praxis Core Prep to your courses menu -- however, you can access it from this link: https://www.khanacademy.org/prep/praxis-core, or by navigating to it from the courses tab in the top left corner of the screen (under 'Test Prep').

I hope this helps! Please let me know if you have any further questions!