How to size button element to make it smaller

Hey @markos84uk, Thank you so much for your response. I originally thought to do this but was having difficulty creating it. My goal is to have the circle turn white when you hover over it. I was unable to get the images stacked on top of each other and stacked on top of each other vertically. This is what im trying to recreate:

If you scroll down you will see the side navbar appear. Would you have any suggestions on how to do this using .pngs…that is the stack sizing the circles for the navbar using images and stacking them?

Thank you again,
Dom