Shooting with two eyes open allows for better balance and orientation while holding the Firearm.
It also adds for a better field of view. With one eye closed you are basically blind to one side. Therefor it's good to practice with both eyes open for defensive shooting. However, it is usually easier to score better on targets with only 1 eye open. So for me, for leagues it's one eye open, for other practice it's two eyes open.
How do you do it? It just takes practice and getting used to. One eye (your dominant one) will provide most of the focusing. With a little practice, you still see the sights and target clearly with your dominant eye while the other eye fills in depth and your field of view. Awkward at first but not bad with a little practice.
Hey Sport45, are you dominant in one eye or eye neutral (is that possible???)