Dynamics 365 Enterprise licenses does not include general purpose Power Apps capabilities. Dynamics 365 Enterprise users will continue to be able to run apps and portals that extend and customize the licensed Dynamics 365 application, as long as those apps and portals are located in the same environment as their licensed Dynamics 365 application. Custom apps or portals outside of the Dynamics 365 environment will require a standalone Power Apps license. In short, If a user A has only dynamics 365 license applied, then A can be added only to environments which has at least one Dynamics 365 App installed. Read more here.