How to Make a progress bar go up after two objects collide.

Could someone explain how I would use OnCollisionEnter with this progress bar? I’m trying to get this progress bar to fill up after a task (i.e. putting food into a dog bow) is completed. I have the food game object and the bowl game object and when they collide I want the progress bar to fill up. How would I go about doing that? Thanks!

Have a look at this, this should answer your question.