The site is http://opensourcetreadmill.com/
Enter your zwift paces so the actual speeds will match your future runs in zwift. The web-page will “store” these preferences as a cookie.
Enter a warmup, interval, steady state or cooldown using the tools provided
download the .zwo file and move it to your workouts folder. The instructions for this have been detailed elsewhere.
You must run ZWIFT from the same computer you stored the .zwo file on. These workouts will carry-over to all your other zwift devices.
Let me know how I can make this better. This is really fresh and new. And, quite frankly, It may not work at all. But it works for me.
All distances are in miles. Sorry.