How can anyone be a part of the New Covenant if they are not part of Israel or Judah?

Jeremiah 31:31-33 ESV "Behold, the days are coming, declares the LORD, when I will make a new covenant with the house of Israel and the house of Judah, (32) not like the covenant that I made with their fathers on the day when I took them by the hand to bring them out of the land of Egypt, my covenant that they broke, though I was their husband, declares the LORD. (33) But this is the covenant that I will make with the house of Israel after those days, declares the LORD: I will put my LAW within them, and I will write it on their hearts. And I will be their God, and they shall be my people.