[jQuery] popup form(please help me)

i want create one form for add catagory to database with php and
jquery.
when i click on one link,ex:"add new catagory", show this form and
when user add new catagory, some select menu refrash and show new
item,and in this form user can edit catagory title also.

i am new in jquery,please send your full source code and explain step
by step.