quest: Leoma's sightFollow

I'm trying to finish this quest Leoma's sight. Leoma wants me to combine the plant and the elixer to make a potion for her. I have the componets and they are in my inventory I click on one to place it on the mouse point then press F4 because that's what my keyboard is configured for the use command but nothing happens. Anyone do this quest? How do you combine?

Try placing the component on an empty slot like you would do a spell then hold down your use key and at the same time hit the slot number. That should work. Good hunting. :)