What did the horse leader order, and why did he do that?

From the text:

When it grew towards evening, the master horse ordered a place for me to lodge in; it was but six yards from the house and separated from the stable of the Yahoos.

The master horse ordered a place for Gulliver to sleep. He ordered that Gulliver sleep separate from the house..... and separate from the Yahoos. In this way, the master horse acknowledges the difference between Gulliver and the Yahoos, who both the horses fo and Gulliver found offensive.