Assuming you are talking about after the film has been applied to the window, there are a few things that need to happen before the tint is completely dry.
First, all of the water needs to evaporate from between the film and the glass. This usually takes 24-48 hours, but can be hastened with the use of a heat gun or hair dryer set on low.
Once the water is gone, then the curing process can begin. For many films, this just means exposure to sunlight, which activates some chemicals in the film and causes it to adhere more strongly to the glass. In general, you should wait at least a week before washing or rolling down your windows, though for best results consult your tinting professional for their specific recommendation.