My friend just installed one on his and l felt that this was impossible because of the engine size. l have not seen his Fiat yet because he said he did so this week and I am not sure till l see. l have a Punto just like his, please can you tell me if it is possible? If it is possible what should be the size of the turbo?

you can fit a turbo to any engine, you will have to have the compression of the engine lowered which will require some engineering work.
you will then need a turbo,wastegate and all pipework to fit.
your;e best bet would be to do a Internet search of turbo company's.

Yeah its pretty easy to do most of the bits you need can be found in your local breakers yard or on ebay.
You will need to lower the engines compression as a naturally aspirated engine is much higher than a turbo charged engine.
Adding another gasket to the head should be enough

Why bother?
The very first thing you will do by fitting a turbo to it is invalidate your insurance policy.

Just buy a decent car instead.

leslie is spot on, but dont bother yes you could fit one on your car but really its only a 1.2 the smaller the engine the less it can handle, a turbo might blow it up. fiat uno 1.4 turbos were prone to blowing and the renault 5 aswel, get atleast a 1.6 if your going down the turbo route