It’s a very easy concept, I don’t think a tutorial is needed. You’ll need to set up an email address on your website administration panel. Are you using cPanel, or another? If cPanel, click the “Mail” icon >> “Manage/Add/Remove Accounts” >> “Add Account” at the bottom of the page. Then, select an alphanumeric address that only you know (if anyone else sends mail to this account, it will be posted on your site, so you don’t want anyone to know its address). A sequence of capital and lower case letters, numbers, and symbols is best. Do the same for the password.
Then, on your wp-admin interface, select “Options”, “Writing”, then go to the second section of the page titled “Writing by e-mail” and enter the email address you just created as the “Login name:” and enter the password for it under “Password:”. Your mail server should be something like “mail.<your domain>.com”. The port is 110. Then select which category you want the posts to go to. Let me know how it works for you.
~Jonathan