You should use a torch lighter ideally, but a regular lighter should still do the trick. Try keeping the lighter on it for a while though, the whole point is that Salvia needs to be lit really hot for the desired chemical to be activated, which is why a torch lighter is often recommended (and which is why joints and blunts are not effective). But if you have to improvise, burn the hell out of it with a regular lighter, take a huge rip and hold it in for as long as humanly possible and you'll trip balls.