Turn your computer on and go to your favorite browser. Insert the following address: http://www.payphone-project.com/mailboxes/.
Once on the site insert the zip code you are mailing from in the search box that says "insert a 5 digit zip code." It is located on the top right portion of the screen.There is a second zip code search box about six inches below it. Be careful though, just above the second zip code search box is a Google search box - ignore it.
After you have inserted the mailing from zip code into the "enter 5 digit zip code" box click go. Your search results return quickly. The initial search returns simply give you the locations of all mail collection boxes in the zip code; the site provides you with a map.
Print out the map if you are unsure of the site. Take your stamped, addressed letters and drive or walk to the post office box you have chosen. Deposit your letters in the collection box.