Display Check Marks

Hello everyone,

I'm fairly new to Storyline, but I'm learning quickly thanks to this community. I have built a scene from a simple template I found here. I would like to display checkmarks on each tile on the right side once it has been visited. Can someone point me in the correct direction on how to do this? I'm attaching my file here so you can see what I have. I also have it in Review 360 if you'd like to take a look. LAD | Review 360 (articulate.com) 

Thank you in advance for your help! It's appreciated so much!