Logitech g402 does not work at fortnite?

The Logitech g402 has 8 keys but I can only use 4 of them for fortnite what do I have to do to make the others work?

If the 4 additional keys are not automatically detected by the game:

You must assign / link the mouse buttons in the Logitech Gaming Software to a keyboard key

These buttons then assign an action in the game.

Thanks works