This is a simple, 3-steps process:

1. Athletes should use Garmin Connect to download their workout files (.TCX or .CSV) on their local computer
2. Athletes should attach the downloaded .TCX or .CSV file when saving their workout in AthleteMonitoring.com
3. You can then use Training Peak's WKO+ software for Mac or PC (free trial available for PC available here ) to open the .TCX or .CSV file uploaded by athletes and analyze the data.