To unlock the Como Te Llama trophy in Shadow of the Tomb Raider you must locate and pet five llamas. The place to do this is in the Hidden City so you'll have to progress through to the game's major hub area before you can get it.
There are llamas dotted around the inhabited regions of either side of the river. Approach and pet five different llamas to get the trophy. Unfortunately you can't pet the same llama twice for this trophy.
Here's an excellent video guide from PS4Trophies
if you get stuck.