how do you throw a sinker

You throw it just like a 2 seam fastball…except (Now I’ve seen 2 variations), in one variation the fingers are just off of the seams to the inside of the ball (Side closest to you) and you pronate on release. The other is straight 2 seam with a pronate on release, sort of a screwgie release. The biggest thing about the pitch is it is a “feel” pitch. You have to work it, make sure you hand starts behind the ball and you pronate over the top. Throw it when you play catch just like when you work on your change. You will see it start to move in and down on the righty (If you are a righty) when you become successful.
Good Luck!