what are the procedures for filing a community property agreement in WA state

If you and your spouse have just completed and signed a community property agreement, you will want to file it with the King County Recorder's office (as your listed as living in Auburn, Washington). You will find plenty of information on their web site about how to file documents: http://www.metrokc.gov/recelec/records/.

If you are exercising a community property agreement after the death of a spouse, you may need to record the agreement in any county where real property subject to the agreement is situated, and the surviving spouse will generally have to file an affidavit stating that the agreement was valid, that all debts and taxes have been paid, and that there is no probate proceeding.

As always, I recommend that you consult with a probate attorney if a spouse has just died, and/or visit Richard Wills's excellent self-help web site www.wa-probate.com.