In TGC 2019 both players select the same course and optional course conditions.
Make sure both have the same course conditions and gimme settings (if not using default).
Recommended: Click -> Change Custom Rules and switch on -> Turn Order.
When the course has been selected and options are configured click -> Create Match.
Edit the player tee if you want to play from a different tee.
When ready click -> Begin Round.
When on the first tee both hit <ESCAPE> and click -> Groups.
In the Game column on the right click -> Add Player.
Next Click -> Add Rival.
Find your friend on the list.
Add each other to the round.
Both tee off when ready. TGC will sync after both hit the first shot.
TIP: If you want to see your opponent character actually making a swing switch on Turn Order Animation from the Main Menu -> Settings -> Social.