1.how to use gps?
That depends on which device/carrier you are working with. It varies.
2.which device is use to connect gps?.
My best suggestion is the Motorola i730 from Nextel. It has GPS APIs that you can actually use (after you jump through a lot of hoops to become a Nextel developer).
3.any free service provider available to find location?
It's not possible to do this for any arbitrary device. (Unless you happen to operate a 911 call center and the government forces the carriers to work with you.)
William Frantz
http://sprintdevelopers.com