Oops! At the time you paired your Garmin Connect with Wikiloc, you did not activate the "Courses" permissions.
In order to send trails, go to Settings > Garmin Connect, and under the section "Send trails from Wikiloc to your Garmin GPS", unpair and pair again, making sure "Courses" is active.
Create your Trail Lists
Organize the trails you like in lists and share them with your friends.