1990 Honda Civic How do I remove the coolant overflow tank?

I just bought this car and I take it to get the oil changed and they tell me they see antifreeze coming from the water pump and that it will be 500 dollars to replace the water pump and timing belt to be on the safe side. Too expensive. Anyhow, I went to pour antifreeze in the resovoir and it all just drains out the bottom onto the ground underneath. So, Im thinking it might just be a cracked tank. How do I remove the overflow tank?