Turn it off completely (hold the power button down for 10 seconds even if it seems to already be off).
Don't try to charge it anymore.
Maybe leave it somewhere with the lid open and facing down so water can drain out of the keyboard, although if you've already futzed with the laptop enough to see if it would charge or turn on, I don't know if this matters anymore.
Let it sit somewhere dry for a while and give it time to dry off, maybe a couple days.