The guys over at Payette Forward have made a great video walking you through the various steps needed to start using new fonts on your iPhone. So I decided to pay it forward and give them a link here.
I'll include the steps below, however, in case you'd prefer to follow along here with us.
When you select the globe icon at the bottom left hand side of the screen, you can switch between the Facemoji keyboard and any other keyboards you might have installed on your iPhone.
Make sure the Facemoji keyboard is selected.
Facemoji will try to get you to give it full access to your information or buy its premium version. (What app doesn't do this!) You DO NOT have to grant it access or buy the premium version. There are many free fonts that will be available without paying a premium fee.
You'll see a gray bar above your keyboard. Scroll left and right to find and select the font you want to try out!