I’m assuming you will just link whatever account you already redeemed your ultraviolet copies with (e.g. Vudu), and they will show up.
That's exactly how it works. It took about an hour after linking my Vudu account before they showed up on the Movies Anywhere site and iTunes.
My Vudu account has yet to work. It'd be nice since I've got a lot of Ultraviolet DVD/Bluray codes there, but generally don't bother going to Vudu for much else.