Alrighty, then, after a short delay, we have both our contestants' pokemon (keep in mind that you won't have to send your pokemon PM in your average battle on here. This is just a special case).
Our battlers both throw out their pokemon at the same time, and they open up to reveal...
On Underscore's side of the forest arena, we have a male meditite with pure power (maybe I should get a meditite. I've seen a few people with those xD)

And on Poke's side, we have a female eevee with Run Away.
The referee comes out onto the arena and flips a coin. Heads would mean Poke goes first. Tails would mean underscore goes first. The coin is flipped, and.... It's tails! Underscore goes first.
Ok, some things you guys might want to be aware of, since it's your first time. You may or may not already know some of this stuff.
In this ASB, during each round you command your pokemon to use three moves in succession. For instance, since Underscore goes first, he would post in here saying that Meditite uses Bullet Punch ~ Fire Punch ~ Toxic. Bullet Punch would be used the first turn, Fire Punch the second, and Toxic the third.
You can choose to use "combos" of moves if you like, but the total amount of moves used per round has to be 3. So, for instance, if you decided to have meditite use Bullet Punch + Fire Punch as a combo, that would count as 2 moves, but both would be combined into some sort of move that the ref would have to interpret.
There are more things you can do that you will learn later on, but for now Underscore posts his commands first. Don't hesitate to ask questions.