Flat ownership after fatner's death

Hi, myself Santosh and my mother resides in Virar (Thane -Dist). The flat is in the name of father who expired in 2007. The agreement is in the name of my father and also the maintenance bill comes in my father's name. I want to transfer the flat onwership in my name. Please guide where and whom to shall i approach with which documents. It will be extremely helpful to me.