"Do Signposts explain how to get there?"
I'm not sure exactly what you mean, here, but here's how I treat Signposts.
Let's say you have a Physics domain. If you look at the four appreciations under Physics, you will, of course, see Understanding, Doing, Obtaining, and Learning. If you look at them spatially-that is, as all four existing at the same time-then you will point to one of them as the problem. This one is your story's Concern.
For example, if the conflict of exploring the mystical island is that your characters are being chased by a monster, then you will see "being chased by a monster" as coming from one of these corners. Does being chased by a monster come from a misunderstanding of something? is it happening because of something the characters were or were not Doing? From an attempt to learn or gather experience? From trying to obtain something, or maybe from the monsters attempts to obtain the characters? All four of these areas-misunderstanding, doing something, gathering experience, and obtaining-are all present in the story at the same time. And it's the imbalance between these four that creates conflict. But spatially, you will feel this conflict tied most strongly to one corner.
Now if you view the quad temporally, you will not see all four as existing at once, but as existing one at a time and in sequence. Where a spatial view sees how things are laid out, a temporal view will see how things are played out. And instead of saying out of four corners, the conflict comes from this one, you are saying the conflict comes from this corner first, then that corner, then that one, then the last one. This temporal view gives you Signposts. So signposts explain in what order you look through the appreciations of the quad.
But the appreciations aren't just sources of conflict. Each "vertical" level of the table gives you a different type of appreciation. The domain level is the genre, or purpose. In short, the Domain gives you the Purpose of the story. But the Concern level is Methodology, or the type of elements one will engage to achieve a purpose. In other words, Plot.
So to answer your what I think you’re asking, Signposts describe the path taken through the quad as the perspective views each in sequence, and also shows how the mind engages in each area as an effort to solve the problem. Any path through the quad is valid, so the Signposts don’t exactly describe “how to get there”. They just describe how these characters in this perspective “got there”.