Yes. Go to your event editor. After opening up your "Calls to action", you can just click on the "<button>" menu. 

You will see a button wizard, where you can set:

Link Url: You can set the destination here for your button
​Main text: What the button should say, e.g Buy Now Secondary Text: If you want to add something underneath the main text, e.g $25 - today only
​Color: Set the background color for your button
​Size: Choose between small vs regular
​Icon & Position: You can add an icon to the top/bottom/left/right of Main text

Once you are done you can add the button. If you want to change something, you can click on the newly created button.