My grandmother died. Dad’s brother didn’t tell me about the will. I was told that my name was on it because my father died. What can I do?

My father died before my grandma. When my grandma died, she named my brother and I in the will. I am the oldest child. My uncle contacted my younger brother and made him sign a piece of paper that I didn’t know until know. He gave him $500. I didn’t know anything about this until now and didn’t know such will exist. My grandparents properties including million dollar home and acres of land are from another country but my father and grandparents live in the US. What rights do I have?