Hey @Robii,
Start with some basic research about the exam.
Read some blogs and watch a few videos about AWS
Take up a course, there are many e-learning companies that provide amazing courses(Edureka has one as well, which is pretty good)
Experiment with the services provided by AWS(proceed with caution), learn things practically
Give a few Mock tests to get confidence
Finally, you'll be good to give the exam!
All the best :)