There are two layers to tint usually, did they come apart? If not then there's a how too on google.
First you put a tarp or trash bag down so you dont get the floor covered when you spray. You need to soak the tint in ammonia on a sunny day and it will make the glue release. Then you just peel both layers off at once..
If not then theres a lot of scraping I think.
Edit .. heres the link i spoken of.
http://www.tintdude.com/remove.html