How do you bleed water system on saxo vtr?

'water system' I assume you mean the engine cooling system. It is straight forward but there are several steps and things to consider/be prepared for......

Get the Haynes manual for Citroen Saxo. Read the section for changing the engine coolant thoroughly so you know about all the steps before you start. Assemble the consumables you will need, remember that engine coolant can damage paint, and make up a temporary coolant reservoir out of an old plastic bottle.... A container to catch the old coolant is useful, a hose pipe/water for flushing system is useful, decent coolant is useful (you get what you pay for), plenty of time is useful (some of the pipes you have to disconnect may take some shifting), and finally with all due respect, some DIY skills/aptitude are essential for the fiddly bits. Otherwise you will end up with air locks and overheating of the engine and require an extensive paint touch up