How to programmatically change the image in an axes in a guide code?

So I am using guide to assist me in some few things but after that I do a lot of things programmatically. Currently, I am stuck trying to figure out how to change an image in an axes programmatically in a different function. All I wanted to do was when I press a button, once completes its task it would change the image from x image to y image on a specific axes