The absolute requirements for becoming
 a Mason in Washington State are:

Be at least eighteen years of age.
Have the senses of a man, especially those of Hearing, Seeing and Feeling.
Be a believer in a Supreme Being.
Be capable of Reading and Writing; and
Possess no disability in his body that would render him incapable of conforming reasonably what the Degrees respectively require of him.

To join, all you have to do is ask a Mason
(preferably someone you know or at least who lives or works nearby).
If you live in Washington State and you don't know any Masons in your area, please send a message to
  V.W. James F. Brady III and he will be very glad to help you.

If you don't live in Washington State, you need to contact your State Grand Lodge, because each State Grand Lodge Jurisdiction sets its own minimum qualifications. We have some of the Grand Lodges e-mail addresses in our Links page. If you don't find your State Grand Lodge listed, please send a message to V.W. James F. Brady III and he will direct your request to your State Grand Lodge. 

Hope this helps.

Sincerely,