To set up the API that automatically draws data from Garmin Connect to Swim.com, you'll need to have a Garmin Connect account
Open up the Swim.com app on your mobile device and touch the device menu icon in the upper right corner of the screen. On the device type drop down, select Garmin. Select the connect button and you will be directed to the portal in which you will input your Garmin Connect credentials and agree to data sharing terms.
Upload .fit Files
To upload a .fit file from your computer, go to https://www.swim.com/upload
There is a drag-and-drop option on this page or you can click the drag-and-drop box to open a browse menu. Please note this tool only accepts .fit files that are in the Garmin proprietary format. It will not accept .fit files from Suunto, TomTom, or other devices.