help please! on renewal of EAD card

I want to do the EAD extension by myself. What documents should I provide to INS? as I know that I should fill a I-765 form.
Should I send 2 photo????
In the I-765 form,
first item "Renewal of my permission to accept employment(attach previous employment authorization document)" what is the "previous employment authorization document"???? is it the letter sent to me with my first EAD card? or anything else?
thank you, thank you, thank you.
Any information will be very appreciated!