Linking to a phone dialer in Muse

In the new videos about how to create mobile versions of your site, both instructors show that you can add a "click to call" feature to the phone number. This allows the person visiting the site to just tap on the phone number to bring up the phone's dialer. However,  neither one shows how to do this. I've looked in the links menu and there is no option for a phone dialer (and yes, I'm in the phone version of the editor). How do I do this?