Like many things in life, it can be as simple or complicated as you want it to be. Get a bow thats a comfortable weight to shoot, a decent string, glove or tab, arm guard, & some arrows.
Pull it back to the same place every time, point it at your target and let go. If you hit right, aim left next time.
We have to have something to talk about so you can read for years on speed, anchor, back tension, amount of limb reflex, whats a real longbow, aiming styles, limb material, blah, blah blah...
You can cherry pick what you want as you get into it. The basics are 90%.