Set threshold in Garmin Connect
It is important to set your thresholds correctly before training so that your workout targets will be correct. Your Functional Threshold Power (FTP) can be set in Garmin Connect and then sent over to your Garmin device using the Garmin Connect app on your smartphone or from Garmin Express on a personal computer.
Here's how to set your FTP in Garmin Connect.
In the Garmin Connect App
Access the menu by selecting More at the bottom right.
Select Garmin Devices.
Select the device name.
Select User Settings or My Stats.
Select Power Zones.
Input your FTP value.
Tap the return key on your keyboard (for Android) or tap Done (on IOS).
Exit out of the app settings by using the back arrow (upper left).
Sync your device.
In Garmin Connect Web
Sign in to Garmin Connect from a personal computer.
Click the Watch icon in the top right corner.
Select Device Settings under the desired device.
Select User Settings .
Under Power Zones, set your Functional Threshold Power value.
Click Save Settings.
The updated FTP value will now be transferred when your device syncs using Garmin Express.
Device settings cannot be adjusted through Garmin Connect web if the device supports Real Time Settings. For more details, see Garmin's article here.