You can review the exam guides to find out what you will be tested on - each guide includes documentation links, you can use those to help you prepare, and they are used to validate the exam items themselves.
You will also need to take training as part of getting your VCP - the courses come with student guides as you would expect.
Read more about the training, and access the exam guides, through this page: VMware Certified Professional 6.5 - Data Center Virtualization (VCP6.5-DCV)
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VMware Training & Certification blog
