Hi! You can find so many free tutorials on the web. The ones by Paul Wilson are particularly useful. 

Hi! You may want to check Learning Hub on the Adobe Captivate website for free resources. If you are looking out for a certified course, then you may consider Adobe Certified Professional: Adobe Captivate course by Adobe. Currently, it is unavailable though as it is under upgradation. Keep checking the Adobe website. Additionally, you can explore the new Adobe Captivate by downloading the trial version from the website as well. Nothing teaches you more than self-exploring!  

Explore, be adventurous. I never took any Captivate training but have answered thousands of questions everywhere, and offered a lot of personalized trainings. Know your strengths and weaknesses, that is always the core topic on an intake conversation about a possible training, based on projects developed by the trainee.