I have a small block Chevy. The hole to the left below the water pump is leaking. How do I stop that from leaking?

That small opening is a "Weep h0le" for water to escape when a internal seal ruptures, it's to let you know there is a breach. Then you have two options, rebuild the water pump, or replace it. The second option is the less aggivating option, just buy a new pump.

If this is a water pump on your race car, buy a Meziere water pump

Bob