A course I created for a run in Garmin Connect won't synch to Venu 3

I have created a simple trail run course in Garmin Connect. It won't sent to my Venu 3 watch. On the app it says no compatable devices, but the venu 3 is synched (have tried disconnected and re authorising the watch). On the menu for training calendar on the watch it says I need to down the training calendar but it's not clear how to do this.