Your going to need either a maul or an axe. A maul has a wider head and is heavier making it ideal for splitting wood but an axe can be used for smaller jobs. sharpness inst all that important for a job like this as our not cutting the wood. You're splitting it. You're also going to need a good source of wood. Seasoned wood splits easier but this does mean you'll have to stack it twice. Never attempt to split wood with nails in it. Its bad for the axe and potentially for you if it comes flying out.
Put the piece on its end on a chopping block if one is available or on the ground. Using he ground has a chance to dull the axe blade however. Make sure that you position yourself so swinging with straight arms the blade will hit the centre of the wood. Make sure not to overreach. Coming up to short your blade hits the ground and its not too bad but if you overreach the handle will hit the wood and oo much of this and you'll need a replacement.
Its good practice to aim for the same spot every time even if you don't always hit it over time this will improve your aim. Also make sure to let the weight of the axe do most of the work not your own force. this will stop you getting tired as fast.