Whenever a nontoken creature you control attacks, you may pay {W}. If you do, create a 1/1 white Kithkin Soldier creature token that's tapped and attacking.
The token enters the battlefield attacking. It doesn’t trigger “when a creature attacks” triggers and is not subject to restrictions on declaring attackers.
You choose which player or planeswalker the token is attacking. It doesn’t have to attack the same player or planeswalker as the creature that caused the ability to trigger.