the cable joins inside the drum. Its quite tuff to pull off. I normally take the shoes off and use some mole grips.
It's easy if you first fully slacken the handbrake cable, which is (according to eLearn) part of Fiat's official procedure for changing the rear shoes.
It's a good idea to readjust the handbrake cable anyway after fitting replacement shoes (particularly if not OEM parts), as manufacturing tolerances in the handbrake actuating arm on the shoes could affect the cable tension.
If there isn't sufficient slack in the cable when the handbrake lever is fully released, the self adjusters won't work properly.
New cables can sometimes stretch initially, but once settled in, handbrake cable adjustment is almost never required. If you get a long pedal or have an ineffective handbrake, it's far more likely to be a stuck shoe or self adjuster.
Adjusting or replacing the cable in an attempt to solve a rear brake issue is almost never the correct thing to do. Generally they need replacement only if seized or frayed (both of which can occasionally happen).
Unless adjusting a very recently fitted cable which has settled in, I'd never adjust the handbrake cable without pullling both rear drums and checking everything is as it should be.