How to change Language Settings

hi all

i have some prblem

i have a page for Entering Employee's Basic Information. i have arround 10 text boxes for entering his first name , last name , age, gender.. and bala bala.

on top of my Page i have 2 radio buttons. One English and one Arabic. by default English radio button will be checked. If user clicks on Arabic radio button, then all text boxes should take entry in arabic language automatically. how i can do this. can any one help me
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