Typically you have a black plastic cover on the "back" of the alternator (ie the opposite end of where the aux belt is driving it)
That cover either just clicks on or the terminals poke through and you have to undo the electrical cables first and then unclick it, I can't recall.
Stick your camera phone in there, take some pics and you'll figure out what to do.
So the plastic cover just clicks off, no big deal.
Then you need to unscrew/unbolt the regulator and that depends on your model of alternator I believe. Check which one is mounted on your car and look it up in a catalogue.
No big deal, but mine had a bolt in there I just couldn't get a socket around without hacking away with a chisel at the regulator unit. I guess I just needed to commit at that point
So I did and when fitting the new regulator I replaced that bolt with one with an allen head so I could do it up easily.
I found it not overly difficult (it only a few bolts and screws) but very awkward, not a lot space to move your arms around and looking through a mirror to try and see past your arms what you are doing. Getting your position right under the car seems key.
With the alternator on a bench anyone would find it very, very easy.