HI, you would have to apply for him as a common law partner, you would apply outland through any Canadian consulate in the U.S, just pick the one closest to him. Please note that you would have to prove a strong relationship together, and show that you have been living together and share certain things like bank accounts, leases, property, etc..you have to prove a real committed relationship. You also have to show you have lived together for one year continuously. They don't just hand out Canadian PR's to every Canadians boyfriend or girlfriend.
Also please note that your boyfriend would likely loose his U.S Green Card if he got a PR card and moved to Canada, he should be aware of that.
Please see this link for all application links, and info, read the whole page carefully.
Also since your bf has a green card he can visit Canada for up to 6 months without any need for a visa.
http://www.settlement.org/sys/faqs_detail.asp?faq_id=4000444