Pardot API v5

Hi, 

I'm currently trying to call this endpoint in a sandbox environment:  (api/v5/prospects/do/upsertLatestByEmail).

I'm getting the response that the endpoint does not exist. I understand we need to enable access under pardot settings for API v5, but haven't seen any clear documentation on where this is. Has anyone successfully started using the v5 endpoints yet?

Thanks very much for any assistance.