You can get Windows 10 Enterprise through the Prime portal through CSP buy purchasing one of the following SKUs:
1. Windows 10 Enterprise E3
2. Windows 10 Enterprise E5
3. Secure Productive Enterprise E3 (which comes with Windows 10 E3, O365 E3, and EMS E3)
4. Secure Productive Enterprise E5 (which comes with Windows 10 E5, O365 E5, and EMS E5)
More details about Secure Productive Enterprise can be found here.