I would like thanks Amy Marrich, T. Nichole Williams and Linux Academy.
First step was to go through the OpenStack Essentials course and deployed Packstack on CentOS so I can practice.
Next, I followed the OpenStack Foundations COA course and it covers all the aspects of test and definitely the best course there is but need more videos on heat and troubleshooting.
I created a text file containing commands for lectures, hands on Labs and final lab, this made things easy to revise a day before the test.
Lastly watched and practiced the final lab from OCM100 course.
Key is to practice, practice and practice the commands and know how to do the same configuration on Horizon.