To amplify a bit, if you want to use the aid as a command instrument, you dial up the magnetic ground track outbound from the reference VOR station (location A in Paco's example). 'Command instrument' just means that e.g. you fly right when the needle is deflected to the right. For example, if the magnetic track from A to B is 200 deg, dial that into the omni bearing selector (rotating scale), then fly (or intercept) the track ('radial') from B to A keeping the needle centred.
That's all very simplifed, and references such as those noted earlier are well worth a read.