Funny you would ask. I hadn't really thought about it, but I haven't bought magazines, newspapers or CDs in years. I goto the web for all that. I bought CDs in the past where I only liked one song. Now I can just buy the songs I want.
All the magazines I've ever liked are online and if they weren't, there are site out there that are similar enough.
I wouldn't be surprised if there even are printed magazines in five years.
To answer your question, I would goto the website for the magazine you want to subscribe to and I'm sure there will be a link to subscribe to the print edition, directly from them.