How do you install trailer hitch on 2004 Mazda MPV?

I wouldn't since the frame is designed to absorb impact rather than resist impact which is best for towing. You will have very limited tow capacity, 3000lb per Edmunds.com. Pickups and other full frame rear-wheel, four-wheel, and all-wheel drive vehicles make much better towing vehicles. I have heard that dealerships even have issues putting these tow hitches on the MPV; probably because they are trying to secure it, and there's no meat to the frame. Once you have it on, be careful. A base model 2004 Chevy Silverado has 8500lb of towing power compaed to your 3K. You should not tow another vehicle or anything heavy.