Hi,
The Databricks Certified Generative AI Engineer Associate exam information page mentions that there is a series of self-paced courses in Databricks Academy.
You can login to Databricks Academy from this page: https://www.databricks.com/learn/training/login
Once you log in, search for "Generative AI Pathway" using the form at the top:

That learning plan includes the four classes that you will have seen mentioned on the exam info page:
- Generative AI Solution Development
- Generative AI Application Development
- Generative AI Application Evaluation and Governance
- Generative AI Application Deployment and Monitoring
The self-paced courses are free. I hope this helps!