I don't know anything specifically about copaiba, but I think that essential oils can be prepared by steam distillation. You put your stuff in a flask with water, and distill at 100 C. (This works even though your compounds boil at higher temperatures.) You keep distilling, adding water as necessary, until nothing comes off that is insoluble in water. To check this, you can collect some of the distillate, add saturated NaCl solution, and see if you get two layers. (One being the salt water, the other being the oil. The NaCl helps force the oil into a separate layer.) If you see two layers, you are still getting oil and keep distilling.