Changing focus on UF wristsFollow

Hi,

I have a question. How do you change the focus on the wrists in Underfoot? I know sk, bst, necro and shm all get to do this, but my fellowship members asked me how.

I know it uses the wrist inside the box of latent energies. So the fellowship member tried it but all it did was strip the bracer of its aug and did not change its focus. Is there another component that is supposed to go with the bracer since the box has 2 slots. Thanks :)