You can search on it and find the frequencies. I believe you have to tune-into a couple tenths of a mhz above the actual frequency on some receivers. The decoding programs and "modem" are sold by groups like Coretex

Here's a piece on the general subject: http://www.blackcatsystems.com/software/multimode/fax.html; or, http://www.cruiserswiki.org/wiki/Weatherfax;

You can search the web using "Marine Weatherfax download SSB"