To get OED you have to be a user of a library with a subscription. If you're on a college campus in the US there's a pretty good chance you can get it anywhere on campus because they use IP authentication. I'm not sure how public libraries handle it, but sometimes they are able to authenticate with library card information.

Here's the address we use: http://dictionary.oed.com/entrance.dtl

If it works, then your institution has a subscription. If not, poke around the library web pages or library catalog & you might find information about connecting. If you're in the library ask the reference librarian.