Are you registered for a course? Once registered, the Webex invite will be sent via Tableau's globalservices alias -- you can reach out to them if you have registered already but have yet to receive the info. Typically, the WebEx info isn't sent out until the week prior to a virtual course delivery, so if yours is coming soon, I'd expect the invite email to arrive soon. But again, email firstname.lastname@example.org if you have an existing registration that you'd like to inquire about -- that team handles all training logistics.
Cheers and best wishes!
It has been a few days without a response Colin so I have marked Matt's answer correct (Matt works on our training team). If you should have a follow up question, please feel free to comment here and Matt and myself will be alerted.