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That blow to the cheek that the Bishop gave you at confirmation was to remind you to defend the faith.
That means first you have to know what the faith is.
No appearitions are part of Catholic Dogma.
Here's a place to start: "The Sources of Catholic Dogma". Read it, but don't trust it. But it does have many of the sources. Sometimes what Father Denzinger says and the source don't agree.
Protestants will lie about the Catholic faith; hate of the Church of The Lord is the only thing Protestants have in common.