My Elder brother has illegally captured my Land how to proceed by law

My father registered a plot of land on my Mother's name. Before passing away my mother(with almighty GOD) signed KHARIJNAMA and gave that piece of land in Bihar to 3 brothers -- including me. I have all the legal documents and I have that KHARIJNAMA (thumbed by my mother as she couldn't read and write). But somehow my elder brother whose name is NOT IN THAT KHARIJNAMA did REGISTRY of that land on his wife's name. He also sold part of that land. My father is still alive and has advised me to file case against my elder brother, because my father said that after my mother passed away, now he is the legal owner of that land. And he will support my instance before court or any judicial body. I need your help as I don't know how to start with this case/ whom to approach/ and if my papers are enough or not. Also Land is in bihar/purnia -- Village Tikapatti/ but I do service as senior Technical operator at Tata steel. So where I have to file the case and to whom I should approach.