Two or three drops is what's usually suggested, but if you use more, it's not a problem, just wipe it up. Sweet oil is the same thing as olive oil and will not hurt you. To be most effective in the ear, warm the oil up by running hot water over the bottle or putting it under your heating pad a couple of minutes.
Do not microwave the bottle or the oil. You want it to be only a few degrees warmer than body temperature.