This is a tiny bit complicated. Energy is all around you (in the air, earth, plants, animals, water, etc...). You need to learn the basics which are meditation, grounding, centering, open your chakras, etc... to learn how to harness the natural energies around you. Of course in my mind people also have energy within them they can use, but stronger spells would require harnessing more power.
A secret place isn't needed, but a place that is quiet would be best.
I don't believe knowing your element is necessary, but you are normally harnessing energy from the elements so knowing it couldn't hurt.