Like hash oil? The easiest way that I have seen was to get a pin and dip it in the oil. Then there should be a piece on the end, light the pin with a lighter so it heats up and the oil just drips off the end. Then I usually just put one drop right on top of my weed. It will turn any weed into the best weed ever with just one drip. Otherwise I've heard of special bowl pieces you have to buy in order to vape just the oil.