If you are attempting to answer this question when it’s posed by a Protestant, you have to lay the groundwork. This is not easy, because they usually don’t agree with us on many of these interpretations of Scripture. Still, what it boils down to is that:
Jesus sent the Holy Spirit to guide His Church - John 14:16-17, Acts 1:1-5, John 20:21-22
which is built upon the Rock of Peter - Matthew 16:18
in doing the will of God the Father John 14: 26-31
The Church is the Body of Christ 1 Corinthians 12
It’s made up of individuals, but Jesus prayed that they might be one - John 17
Jesus and St. Paul are speaking to the apostles and the early Church as a group, and St. Paul discourses on the relation of the individual “part” to the entire “body.” Individualism as our modern culture views it is not part of the teaching.
The Magisterium as we know it today is the same object of these discourses, just more developed as the need arose throughout the centuries. It’s entrusted with the same responsibility and mission, towards the same end, transmitting the inspiration of the Holy Spirit to the Body of Christ in every age.
When, as pointed out in posts above, two individuals each claim to be inspired by the Holy Spirit yet are in opposition as to what’s the correct thing to believe or to do, at the maximum only one of them can be correct, and possibly neither of them can be correct. The Holy Spirit isn’t going to go against what Jesus established. So careful discernment is required.