New User trying to use a UI button to interact with objective markers

I'm a completely new user to Unity to the point where I don't even know where to look to learn how to do what I'm trying to do. Any direction or assistance is appreciated.

What I have so far: I am trying to make a top down game designed for use on a mobile device. I have a UI and menu system implemented. I have the map with collisions and a player sprite who is connected to the joystick I put on screen.

What I am trying to do is create prefab objective points on the map that appear in random places and have the player use the interact button I put next to the joystick to activate and complete the objective. Ideally a situation where they hold it down until completed but I'll settle for a press the button and be done scenario.

My issue is that I'm not even entirely sure how to approach the issue. Do I need to make a script for the player sprite that makes pressing the button activate an 'interact' state? Do I make it so the button does something but only if pressed while in the objective area? I'm not sure where to look to figure out how to do these things, any help is greatly appreciated.