How to change water pump?

Hi there,
I'm a learner driver and only just recently got my car off a family friend just to learn to drive in. It has done alot of mileage but it was just a car to get me kick started.
The only problem one day it over heated and I need to replace the water pump. I've tried but being new to this I think I just made a mess.
I was wondering if I could get a step by step guide how to take it off and replace it?
Diagrams would be helpful because most of it looks the same to me.
Cheers