change the window seal / gasket.
Go to a qualified automotive air conditioning technician. == ==
Fix it.
You have to determine the source of the leak then decide on how to fix it.
Silicone sealant.
buy a new window
You cant
replace the glass or get window sealant
You have to replace it. They are designed to leak when they are going bad.
Are you sure you have a leak? Most of the time when using the air conditioner, your car will appear to be leaking water or dripping underneath the vehicle, towards the front.
usually by replacing window regulator.
Get a new car
Look for a vacuum leak.