If you are a pace based runner then you use threshold pace as your training intensity gauge.
The test involves a 30 minute all out effort. At the end of this effort take your average pace in this 30 minute period. Your threshold pace is 95% of your 30 minute all out average pace.
To calculate the same you can go to the zones page of your enduroco account and scroll the bottom. There you can use this handy tool to calculate your threshold pace.
After that you can go to the settings page and save this value there.
Next update this value in TrainingPeaks and you are all set.