If you have a button on your page that you would like to trigger a phone call action (particularly useful if you have visitors that are accessing your site from mobile phones and want to call you) - you can do this easily inside OptimizeBuilder:
First you'll need to add a button to your page. You can style this in the normal way with any of the buttons inside the OptimizeBuilder.
Once you have setup your button, open the link option and set to use the "Link URL" option.
Now all you need to do is enter tel:555555555 where you replace the number with your own phone number. For example if your business phone number is 310 755 7755 you would use tel:3107557755
When a visitor clicks this link, it will trigger the associated phone feature on their computer or phone.