I havent seen or experienced myself but i would say that they woukd be similar to car badges...I would say you'd peel back a sheet to reveal sticky tape, and you'd have to line it up by eye and press it on, smudging it from the center out to get all the air bubbles out. You could probably use tape on the outside to line it up and use a lead pencil to outline the pad. Then peel and stick...if you miss, heat it up with a hairdryer over 5minutes and remove. But probably got one shot at it. I'd maybe heat the tank with a hairdryer alittle just to warm it up, to help it adhere to the tank nicely.
I bought my XSR700 with tank pads already fitted, they seem to be glued.
It can't be that hard to fit them but removing them might be difficult as they stick firmly!
Heating them up as Anthony suggested might help though.