Basically, you're all play God's. Feel free to interact with one another and Roleplay out having godly conversation, arguments and so on. So, essentially what you do is state what you want added or done by your will. So, for example at the start there is nothing but darkness. So a player adds light in the form of a Sun. (Roleplaying it would be preferred) The next player adds planets to bask in the light. The player whom created the sun may now envy the planet and cast fire on it. Meteors rain down on it. Yet another player may decide to cool the planet by adding water etc. and the entire time I'll be illustrating all of it for you.
In the beginning there was nothing. In this realm, nothing had ever been and nothing would ever be..
I've never done this before, so I don't really know what to expect. I was never a big character sheet guy anyway, but as Pathfinder said you don't even have to have a name. Just will something to happen and I'll make it so. As far as I'm concerned the RP has already started, so anyone can go at any time.
If anything, I would just place the general outline of your god. Nothing too serious, just what falls in their domain. Like mine will have stars, wishes, and wonder.