At the start of the game after you walk a little bit, you will be offered an arm wrestling match. The guy will say Ready, and then Fight. On fight, you need to hammer
as fast as possible to win.
If you win you will get this trophy. There is another trophy for winning 5 matches. I tried going against this guy again, I made it through 4 total wins, but the fifth one was too hard for me. You don't have to get all 5 with one guy though, so now I just need one more.
If you do go again, then the game adds in the occasional QTE which for me was