You can easily send email from any computer using EarthLink WebMail. Simply visit https://webmail.earthlink.net/ and login with your EarthLink Email address and password.
Once you have logged in, simply click the Write button to create a new email.
Type out the email address you want to send a message to in the To field and then add a subject line in the Subject field. You can type your message in the box below those fields. There are numerous options available to change fonts, colors, etc in your message as well. When you are done writing your message, click the Send button on the top left under Write Message.