After you have executed your will (signed it in front of two witnesses), you have a couple different options: (1) simply store it in a safe place, preferably an actual safe that is fireproof, and give a couple copies to your personal representative (the person charged with filing your will upon you death and overseeing the distribution of your estate per your wishes) and if you have appointed them, successor or alternate personal representatives; or (2) file the will under seal with a court having jurisdiction. Typically, that court is the superior court for the county in which you reside.
The first option is the simplest, as you just have to ensure that your will is kept safe, or that someone whom you trust has a copy that they can file upon your demise. Basically, you just have to ensure that someone, somewhere can find and file a copy of your will. If a copy cannot be found, it is presumed that you destroyed your will and intended to revoke it, so your carefully drafted estate plan will be for naught.
The second option ensures that the court will have a copy of your will. For a relatively nominal fee (King County charges $20.00), the court clerk will retain your will under seal (it is not a public record until filed for probate) for 100 years.
While pretty much anyone can file the original will with the court clerk, only you will be able to withdraw the will. If a guardian or attorney in fact wants to withdraw your will after, and God forbid, you are incapacitated, they may only do so after filing a motion with the court to do so and showing that good cause exists to do so, at which point the court will issue an order that they can withdraw your will.
The easiest route is the first one, simply ensuring that a couple copies of your will exist so that it can be submitted to probate upon your death.The second route is a bit more involved, but is the surest way to guarantee that your will is available to the court.Only you can choose the best route for your unique needs and preferences.