Dynamics 365 is not part of Office 365. Microsoft has brought its licensing plans and features for various products under Office 365 Administration.
Having Office 365 subscription doesn't mean you'll have access to Dynamics 365. You'll require license for accessing Dynamics 365.
For Dynamics 365 licesing:https://us.hitachi-solutions.com/blog/ultimate-guide-dynamics-365-pricing-licensing/19