You'll find two "FN" buttons on the right side of your keyboard that may seem like they have no input, but these buttons are used to access different "layers" of the keyboard.
Here we see "Layer 0" or the base layer with our "FN" buttons circled in pink:
While holding this button, the next keypress will be accessing "Layer 1" shown below:
There are infinite ways you can configure your layers and you can learn more about setting up your own in the "PCB / Customization" section of our "Getting Started" page!