To be one, ask one.
One of Freemasonry's customs is to not solicit members. New members come to the Craft when they seek us out. If you know a Mason, ask him. He'll be glad to speak to you about our fraternity.
Membership is for men, 21 years of age or older, who meet the qualifications and standards of character and reputation, who are of good moral character, and who believe in the existence of a supreme being.
A man who wants to join a lodge must be recommended by two members of that lodge. He must understand that his character will be investigated. After approval by the members of that lodge, he will be accepted as an applicant for membership in Freemasonry.
The doors of Freemasonry are open to men who seek harmony with their fellow man, feel the need for self-improvement and wish to participate in making this world a better place to live.
If you don't know a Mason, look through the lodges listed and find one that is in your area, and meets on a night that works for your schedule. Use the link to contact the Lodge Secretary and express your interest.