There is no rite by which one becomes a Unitarian Universalist. There is no baptism or formal conversion process.
One joins a congregation by signing the membership book of that congregation and agreeing to its Membership Covenant. The Membership Covenant lays out a member's responsibility to participate in the support and life of that congregation. There is often a signing ceremony, but the relationship is between the individual and the congregation, not the individual and God.
One can be a UU without belonging to any congregation or by belonging to the Church of the Larger Fellowship. The CLF is a recognized congregation that does not have a church building where members worship. Members are scattered across the globe and may live in places where there is no local UU congragation.
If you are interested in joining a Unitarian congregation, look up your national network of Unitarian churches. In the UK, they can be found at www.unitarian.org.uk, for example (this website has links to similar ones in other countries).
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Unitarian Universalist Association was created in 1961.
Universalist-Unitarian Church was created in 1832.
Covenant of Unitarian Universalist Pagans was created in 1985.
Unitarian Universalist Christian Fellowship was created in 1945.
Anchorage Unitarian Universalist Fellowship was created in 1955.
Unitarian Universalist Service Committee was created in 1940.
First Unitarian Universalist Church of Niagara was created in 1928.
Eno River Unitarian Universalist Fellowship was created in 1966.
Southeast Unitarian Universalist Summer Institute was created in 1950.
Knoxville Unitarian Universalist church shooting happened on 2008-07-27.
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