Prepare your brethren... - that is, “as you minister to your brethren the people, by killing and flaying their offerings and handing the blo…

The king’s charge to the Levites.

So kill the passover
In the manner, time, and place, and for the persons it should be killed:

and…

The destruction Josiah made of idolatry was related in more detail in the book of Kings. His solemnizing the Passover is related here.