Selector Switch?

My daughter has a Baumatic oven model No...B187ss-B the other day while rotating the selector switch she heard a matallic noise and then the switch stopped working..on closer inspection we retrieved a brass contact which I think has broken off the underside of the switch,I have ordered a new switch which should arrive in a couple of days,could you let me know how to change over the switch...how is it held in place??? any help would be most grateful.

Yours Faithfully
Dave Ford