Right click the wishbone to activate it. You don't wear it. You're only allowed one magic item to be active at a time, so if you're wearing the strength belt, you lose it (but that's OK). What I like to do is once the WB starts beeping (and I turn off the music when I'm hunting silver) I stop moving. Take a few steps forward to see if it starts beeping faster and at a higher pitch. If not, step back to the start point and take a few steps left. Rinse and repeat for different directions. Once you locate the silver, you can re-activate the strength belt so you can carry more ore back to base.