What does Judges 9:6 mean?

All the leaders and citizens of Shechem and Beth Millo got together and made Abimelech their king, right by the big tree at the pillar in Shechem. Judges 9:6 - Modern Text Bible

(The people of Shechem and a nearby group called Beth Millo publicly declare Abimelech as their king, showing their support for him in a significant, symbolic place.)