I did this on a 1995/1996 ('N' reg) Clio 1.9 Diesel and I imagine it's very similar for the 1997 model (both are Mark 1's). Anyway, it's easy. At the bottom of the wiper there's a plastic cover which...
If the blade is worn out...the answer is a whole new wiper arm. These can be got from Fiat dealers...or usually from Ebay for a fraction of the dealer price. Swapping them is simply a case of lifting...