You should start off the theory =) Then, after acquaintance with basic terminology and notions, you should find a proper broker which will suit your needs in trading. Wanna be a scalper? Np, choose the broker with fixed spreads, as they allow you not to bother about fluctuations on the market because of various events in the world. Wanna be an investor and open long positions? Just choose a broker, which offer competitive conditions for investors, I mean various instruments for fundamental analysis such as economic calendar, sections with significant events and news.
So, here you should dive deep in the process of trading, only then find a broker and open demo account.