In order to teach a Support Talent to another member of your party you must first have a Support Talent at a minimum of level 12. The next time you choose to stay at an inn, a cutscene will take place between the character who knows the Support Talent and the character who will learn it. After this cutscene finishes the trophy will unlock.
It's important to note that only certain characters can learn certain Support Talents, and some (like Edna's Money Finding) cannot be taught to anyone else.
Below is a list of all Support Talents that can be taught to others at the inn once the talent is level 12;
Treasure Detection
Mikleo teaches this to Sorey
Point of Interest Detection
Sorey teaches this to Alisha and Dezel/Zaveid
Luring
Dezel/Zaveid teaches this to Rose
Windstepping
Dezel/Zaveid teaches this to Alisha and Mikleo
Item Ordering
Rose teaches this to Sorey
Normin for the Win
Edna teaches this to Lailah
Fusion
Lailah teaches this to Edna