To earn the "KNOW YOUR PARTNER" trophy in Detroit: Become Human, you need to gather all the clues about your partner Hank during the chapter "WAITING FOR HANK..."
Essentially this means analyzing everything on Hank's desk, including the music player, the phone, the chair, all items on the desk (eight points to analyze in total) and the news articles on the back wall of his desk.
It's not clear yet whether you also need to be in attendance for Hank's confrontation with Fowler, but it seems unlikely. Several options remained locked when speaking with Hank towards the end of the scene, suggesting that there is more to discover. But the trophy unlocked regardless, suggesting that the desk items are what triggers the trophy. You should receive it when you reach the chapter flowchart.
EDIT: Down-votes are fine, but I'd appreciate a comment to suggest why it was down-voted so I can improve the guide.