There are several accounts of how the Unitarians and Universalists developed a set of Principles in 1960 and covenanted as a unified religious association to affirm and promote them. One is The Premise and the Promise: The Story of the Unitarian Universalist Association by Warren G. Ross.
On the UUA.org website, find a sample congregational covenant provided by the Rev. Deborah Mero, interim minister (2000-02) of All Souls Church Unitarian Universalist, Brattleboro, Vermont.
Session 2 of Wonderful Welcome, a Tapestry of Faith program for grades 2/3, also focuses on covenant. You may find helpful resources here as well as activities you could adapt for a slightly older or wide-age range group. The session opens with an excerpt from a sermon by the Rev. Lisa Ward, “From Creed to Covenant,” delivered November 17, 2002 at the Unitarian Universalist Fellowship of Harford County (Churchville, Maryland):
A covenant is not a definition of a relationship; it is the framework for our relating. … This calls for a level of trust, courage and sacrifice that needs to be nurtured, renewed and affirmed on a regular basis. … Abiding in covenant is an art form. A mutual creation.
