Posting from email

Can someone please tell me how to post from and email.
i am in the “Writing” section of the Settings and this is the part i am stuck on:

Post via e-mail
To post to WordPress by e-mail you must set up a secret e-mail account with POP3 access. Any mail received at this address will be posted, so it’s a good idea to keep this address very secret.
Here are three random strings you could use: TpFM27pk, 6LQlcw0j, bkkBCTpi.

what are these “Strings” all about? and how do i use them?
please email me at [Email removed]

Thanks
Scott