How can I get the succession certificate.

Sir my mother had died on 25/4/2016 she had an saveing account in an bank in which she had added my father signature in the account before her death, so my father is also the signature in her account. From this very account she had also made fixed deposits before in her single name. Sir after her death i want the fixed deposit amount to be transfer to the joint account of my mother and father as my mother had already added my father signature. But sir the bank is asking for succession certificate. sir i don;t know what i should do ? so please advice us.