Your primary hexagram is a snapshot of your situation as it stands right now. Its name gives you the theme in a word or two, its judgment sums up the moment and what it rewards, and its image, the picture formed by its two trigrams, suggests the attitude that fits. Start here, and read it slowly against your question before you look at anything else. People are often surprised by how precisely a hexagram like Waiting or Conflict names what they're going through, and that moment of recognition becomes the anchor for the rest of the reading.
Changing lines are the throws that came up 6 or 9. A 6 is old yin and a 9 is old yang: each has reached its extreme, the way midsummer already carries the turn toward winter, so it's about to flip into its opposite. A 7 (young yang) or an 8 (young yin) is stable and stays as it is. That's why changing lines matter so much. They point to the exact places where your situation is already in motion, and their line texts usually hold the most specific, personal advice in the whole cast, whether that's "hold back for now" or "this is the moment to speak up."
Flip every changing line into its opposite and you get the relating hexagram. Think of it as the direction things are moving in, where the current pattern tends to lead if it plays out, rather than a verdict waiting at the end of the road. Often the most revealing part of a reading is the bridge between the two hexagrams: what changes, what stays the same, and what you could do to steer the shift. If none of your lines are changing, there's no relating hexagram, and your primary hexagram speaks on its own. The traditional rules below, in simplified form, show which text to focus on for each number of changing lines.