how to interact with objects

If I were to add an object to unity how can I get my character to interact with it?
What are the settings and code to be able to click on something and interact with it?

Request: I imported a gas station pump and I want to be able to click it with my mouse and it highlight and say “Want Gas?”


Highlighting OnMouseOver:

GUI appearing on mouse click: Create a GUI on mouse click - Questions & Answers - Unity Discussions

Check out the documentation and Google some tutorials on OnCollisionEnter and OnTriggerEnter. This will probably give you a starting point for what you’d like to accomplish.