Join an online dating site. Most sites require that emails can only be sent by paid members. If you don't want to pay for a membership, find a free dating site like Plenty of Fish. Set up your profile and write a bio about yourself (see Resources below).
Search for matches by whichever criteria you choose. That may be by a percentage match with your own profile or a different set of criteria that you set up yourself. Look through the matches that come up in your search to find one that interests you.
Use your account to send a private email to the match of your choice. Most online dating sites have a private email account for members to send each other messages straight to their private inbox. To send one, go to your account page and look for your email inbox. The inbox will have an area where the member can compose an email.
Write the email and send it to the member you chose. Give out only information that does not personally identify you by name, address or outside email address. Until you are sure about the person you communicate with, keep your emails relegated to the dating site's email system. There will be plenty of time later on to be more personal.