It goes far beyond the Nicene Creed. That is just the very first step. You have to accept that the Church, acoss space and time, in the consensue of the fathes and saints, is wiser than you. We all enter the Church with our own ideas and baggage and are not instantly cured of it. It is a lifelong process, and not everyone in the Church submits to it, but if you do, and allow that wisdom to correct you over time, them you can come closer to the mind of the Church.
One person might come in believing that it’s OK to “love” (sleep with) whoever one wants, another might believe that the Church ought to always accept and agree with the teachings of modern science, another might think “being green” is an essential part of bing a Christian, another might think that some practices, like head scarves, are “patriarchal/oppressive”, or whatever. The key thing is to accept the authority of that consensus of the fathers. You begin by learning from your priest and asking him, and looking for other wise people who have ben around a long time. But over time, you are also likely to find that sometimes, a priest or “old hand” has himself gone off the rails on something or other, and you can’t really know that until you learn what hs always ben taught, what all, or nearly all saints and fathers in history, have agreed on. When you see a hierarch contradicting THAT, you’ll know. But fortunately, if you allow for people’s fallibility, and sinfulness, and develop a spirit of charity, you’ll realize that pretty much none of us have achieved theosis, and we, as individuals, don’t know everything. You’re not entering a club of holy people, but of messed-up people, who, hopefully, realize that and are trying to repent as best they can.
