Noob asking for help. implement api calls on a working yii2 application

Hi i’m a total noob in yii2, I need to offer HTTP API access to clients on a working yii2 application.
I was following a couple of tutorials on how to bring HTTP API functions to a working yii2 app, but don’t works! I copied the frontend or backend to /api , modified config/main.php but still all api calls redirect me to the frontend. I need to mess with .httaccess or I missing something?

I don’t need RESTfull access, simple implement some specific functions that will receive input via GET or POST and use the models to get/update data in the DB.