iClosed currently doesn't have an integrated dialer, simply because customers already use various phone dialers as Chrome extensions. Here's how it works.
Navigate to Chrome Web Store and install click-to-call dialer at your preference.
All you need is an app that you may have already, with a Chrome extension dialer that can recognize phone numbers on a web page.
Making phone calls from 
AI Scheduler pages
Making phone calls from 
Global Data
Pro tips
Bear in mind that, even though Chrome extensions will add additional useful functionalities in your browser, but they may also slow down your browsing experience.
In case your iClosed pages are loading too slow, Chrome extension may be the reason. Look into all Chrome extensions that you have installed, and turn them off to keep your browsing faster and fully optimized.