I want use facetime.

Are you having problems when trying to use it ? Do you get any error messages ? Are you on wifi (it won't work over 3G) ?

Using FaceTime : http://support.apple.com/kb/HT4319

Only certain countries have face time available

Online iOS 5 / iPad user interface guide: http://help.apple.com/ipad/5/interface/

Online, downloadable PDF iOS / iPad user guide: http://manuals.info.apple.com/en_US/ipad_user_guide.pdf

Or you can download the free iOS 5 / iPad user guide from iBooks.