Ok. You might want to start with the very basics. HMS stands for Heavy Melting Scrap (or Steel). ISRI is the acknowledged standard for grading metal. With that start here: http://en.wikipedia.org/wiki/Heavy_melting_steel

Truthfully, I would advise you NOT getting involved with this until you have a very good grasp of the importing business. But, that's not advise most want to hear. There is a buyer and seller section on this site you could list with. Also, here's a site dedicated to the import and export of scrap metal. Be prepared to put out some money for listing service:http://www.recycleinme.com/