Hi Erika - It took me a while and quite a bit of experimenting to work this out too.
As long as your coach (or you) have structured the workouts with blocks in TP and only use % Threshold Pace as your target (not HR or similar) then the following should work.
Name and then save the workout in your TP calendar for a future day (this can be the next day or workouts scheduled across multiple future days in your TP calendar). Your TP calendar will then export the workout on the scheduled day to your list of workouts in Zwift.
Then when you log into Zwift on the scheduled day (remember the workout will be invisible before that day) your workout should be ready to select and run to under the Workouts option on the opening Zwift screen.
This works 100% of the time for me and I’ve probably not explained it brilliantly but fingers crossed it works for you too.
Cheers - Alan