Changing the font has to be done inside the precomp. To do this you have to double-click the added precomp layer and change the font on each text layer inside.
Currently the latest After Effects contains a bug where additional steps to change the font might be neccessary. Please, check out the following video to learn more.
This works a little differently than in Premiere Composer (where you can change the font directly in the panel).
Changing Icon using Font Awesome
Some items come with special font Icons. To learn how to change these, please visit: https://misterhorse.com/help/font-awesome