Image: UbisoftOfficial screenshot from Ubisoft.
Yo Soy Dani Rojas unlocks when you choose Dani's look at the very start of the campaign. It only counts in your own solo game, and most players get it in the first minutes.
Start a new solo campaign. Early in La Noche de la Muerte the game asks you to pick Dani's look. Make the choice and the trophy pops.
You cannot miss it in a normal playthrough. If you only joined friends in co-op so far, start your own campaign once to unlock it.