And don't drive the car at all!
You pry the water pump apart by the way. Take out the battery, then the front plastic engine cover. Now you have access to the pump (where the other end of the belt goes). Remove the bolts remember where the long ones go!
Pry apart the pump and there you go. If it's broken it'll be a black plastic impeller and you should either have shards or large chunks of the impeller right inside the block there. Get it all out, go get a new pump & gasket and put all back together. Add coolant and then go get a power flush to insure all the tiny impeller pieces are flushed out.
Keep your eye on the pump & coolant level for a day or so afterward to make sure it's not leaking and you've got it full correctly.
If all goes well, you'll be back on the road.
BTW, I would avoid another black plastic impeller and perhaps a metal one as well. I hear the metal ones tend to leak around the seals... but that's only what I read...
If you can find a white plastic impeller, you'll be set!
