I haven't used it myself, but I understand that you access it via the vSphere APIs.
"The vSAN API is exposed as a Web service, running on both the VMware vCenter server systems as well as the VMware ESXi systems. The API provides access to the methods that you can use to manage vSAN.
Managed Objects for vSphere Management API/SDK are serviced with the vSphere SDK service endpoint(the Web Service URL - '/sdk').
While the Managed Objects for vSAN API are serviced with dedicated Web Service endpoints.
At ESXi side, the dedicated vSAN API service endpoint is '/vsan'. At VC side, the dedicated vSAN API service endpoint is '/vsanHealth'."
I hope this helps.