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Here’s the quick rundown of the overhead position for the snatch and jerk:

• Push your head and chest forward through the arms
• Keep your eyes forward—think about looking through your eyebrows 
• Squeeze the upper inside edges of your shoulder blades together
• Hold the bar over the base of the neck with the arms vertical
• Rotate the arms so the point of the elbow is about halfway between down and back
• Let the hand and wrist settle into a cradle position with the bar in the palm slightly behind the middle of the forearm

Each one of these elements can easily take up an entire longer video itself, so keep in mind this is a very quick look.
 
The rotation of the arms (described here by the orientation of the elbows) is one of those subjects that has been over-complicated and burdened with all kinds of incorrect or ambiguous information and terminology.
 
The same is true to a somewhat lesser extent of the shoulder blade position—the primary historical source of poor instruction on this one seems to either not being telling people what they used to, or more people are ignoring it.
 
And yes, I’m aware that a few prominent lifters look down in the overhead position. Briefly, I see this create problems in balance and stability for lifters over and over again, and don’t believe it offers enough if any benefit to outweigh this, which is why I discourage it; that said, as always, do whatever works best for you.