Obviously we are talking Spanish digital TV, so if you have that already you *may* get a notification that channels numbers/frequencies have changed, "do you want to re-scan" is a common question. If your TV is set to English language it's very easy, just press yes.
Otherwise if you lose your programs, go to menu and use that to re-scan. I think menu systems will be different on TV makes/models so apart from the logic of how to re-scan frequencies I'm not 100% sure. It's what I've seen in the past when the numbers have changed.