Usually takes special tools. The pedals should be removed, the crankset is either a single arm or a 3 piece unit. If its a single, remove large nut on one side of the crank, usually the left side. Then remove the inside cone, the bearings are visible and should be removed. The last is the crankarm itself. It will only come out if thew left side bear is removed. Twist it gently and it usually comes out at the 3 o'clock position.
If its a 3 piece crankset, special tools are need to remove. SAuggest you take it to the nearest bike shop.