LOL @ Paul.....been there done that!
You can do it two ways....
Buy a whole coconut and use the water from it or.....
The way I like it is to grate the coconut meat itself in a bowl and add the amount of water I want for the rice....plus a little extra in case you need it.
Let it sit for about 30 minutes and then strain the water from the coconut into a pot.
Bring it to a boil....add your rice....stir....put a cover on it and turn the burner to low. Should be ready in about 15 or 20 minutes, depending on the kind of pot you use....LOL
I have a special pot that I only use for rice.
If you don't peel all the brown skin off the meat before you grate it....you will have brown flecks in the rice....this is normal and won't change the taste.
Good luck....let me know how it turns out.