The first thing you need to know is basic economic concepts. Like demand and supply and all this stuff. Later on you should learn trading pecularities and choose the financial instrument for trading. Basically, most traders choose EURUSD because it is one of the most liquid and volatile currency pairs. So, you've got to know how this instrument behaves in different market conditions and how to make use of such a behaviour. One of the most crucial thing is money and risk management. This will secure your budget from the absolute loss whatever happens on the market.