Father died leaving behind property want to transfer it on mother name

Hello. I am a 25 year-old man working in private sector. My father passed away recently (August 2017). We are now 3 members in the family. My mother, elder brother and myself. We have a house which was in the name of my father. Though it was built by my grandfather, but after his death, my father got it transferred to himself with my grandmother's consent. We have a signed affidavit by my aunt (bua) who has given a consent about no claim in this house. So I want to know what is the process of transferring this property to my mother's name? Please guide me. Please reply for any further information, if required. Thanks.