If you got mailed your Washington ballot (and still have it), you can either mail it (postmarked ≤ Nov 4), or drop it in a ballot drop box. It took me longer than I liked to find the →
list of ballot dropbox locations← so I'm putting it here.
For physical voters, a hot tip from
txgreengoddess: the results page for googling 'where to vote' (no quote marks) has a widget to enter your home address. Entering your address gives you a polling location, a map, and links to find your voter registration info/etc.