You can use Font Awesome or Google’s Material Icons in Atomic by creating a text area and selecting these from the font dropdown in the Properties panel. Clicking on the icon next to the font dropdown will take you to the icon libraries where you can copy icons and paste them into Atomic.
San Francisco typeface
If you're on El Capitan you don't need to install anything to use Apple's San Fransisco typeface. Otherwise the SF button beside the Fonts dropdown in the app will link you to a place where you can download and install it.
San Fransisco works on iOS 9+ but not on iOS 8 or below, or Android. For all instances where the font isn't installed a fallback font will be shown instead - Helvetica or Arial depending what's on your system.
Recommended Reading: Prototype faster with Icon Fonts
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