I have already played W2, and I'm going to get White or black. I want to get archen for my team, but I don't know if it is early in the game. When can I get him?
You can get it just before the 4th gym. To get it you have to go to Desert Resort then go to Relic Castle. Go left when you get in until you find a quicksand area. Go past that and make sure you do not run because youll fall through. After you get past it, there will be a backpacker guy and he will give you the choice between the cover and plume fossil. Choose Plume and go back to nacrene city and go to the museum and revive it.
So you can get it right before you get to Nimbasa City.
You can get it in the relic castle and chargestone cave