If you choose to buy a fresh coconut, and this is a good choice, pick one that is heavy (fully mature) and shake and listen to make sure it is full of liquid. They can last like this for months.
To break the coconut, you’ll need a little force. (I often stand on the top step and bowl it on to the concrete in the garden, but then I have to go searching for the pieces.) Use a sharp ice pick to punch holes in two of the ‘eyes’ and allow the water to drain away. Then strike it between the eyes to break the shell. Then use a paring knife to prise the white meat away from the shell.