There is nothing wrong with what you have done so far - half the time you don't know what is important until we start pestering you about it. Don't worry.
Since this is our first combat - how do you want to do it? In my game I do all of the rolls. But this is also a free form game. I'll post below what Azax would do and how the numbers work in D&D, but then you need to figure out what is actually happening. And how you want us to post this.
Azax would take off from his forse and fly straight up. Since he has the sharpshooter feat he doesn't get disadvantage from ranged shots. So he can shoot from 600' and not be at disadvantage. If that is 600' UP - it is hard to get hit back. That is the plan.
He gets two shots per turn at 6th level. So he would go up and shoot twice at the group of four. His to hit roll is +10. He gets +4 for dexterity, +3 for his proficiency bonus, +2 for his archery fighting style and +1 for the magic bow. (Note that because of the sharpshooter feat and all of those plusses, he could choose to take a -5 to hit (so still +5 total since he had +10 to start) and then get +10 to damage. I'm opting not to do that.)
When he hits he does 1d8 +5 damage (+4 for dex bonus, +1 for the bow.)
But as an arcane archer he also has a couple of Arcane Shots. He can only do this twice per short or long rest - and he can decide AFTER he knows the attack hit if he is going to use the ability. The one he would use now is:
- Bursting Arrow: You imbue your arrow with force energy drawn from the school of evocation.
- The energy detonates after your attack. Immediately after the arrow hits the creature, the target and all other creatures within 10 feet of it take 2d6 force damage each.
He would likely do this on both of his shots - if they hit. (He would target two separate orcs hoping to kill them all.)
So the result would be: Two attacks at +10 to hit.
If they hit he does 1d8+5 damage and then everyone (including the original target) within 10' takes an additional 2d6.
That is how the math works in fifth edition D&D. You weren't really looking for all those numbers I don't think, but it gives you an idea of what would happen. Sixth level characters can do some cool stuff. Do you want that sort of detail? Is it easier for you if I tell you that or would you prefer to just get the general idea of what I'm doing without all the D&D numbers?
*I will still post in the game thread - this is just to figure out what you want in the game. Plus, the two stuck on the ground may want to slow up his attack since they can't get there as quickly, but I don't know.