Thank you for writing in, first please navigate to Font Manager, and upload your custom font in there.
After you successfully uploaded that font to font manager, you can then add that custom font to your list of font-family
And then on the actual text, please do not use the Content Area element because that has no font controls.
Use the text element instead, it has text formatting and styling options.
On the Font Family dropdown option, choose the custom font that you added from the font manager.
Hope it helps,