If you apply this expression to a layer's position, it would attach the position to the first path point in a shape layer called "Shape Layer 1" with "Path 1":
thisComp.layer("Shape Layer 1").content("Shape 1").content("Path 1").path.points()[0];
Basically you can just apply a blank expression to the value you want to connect to, then pickwhip to the shape layer's path, then add ".points()[0]" -- where you'd replace the "0" with the number of the path point you want to connect to. It's probably helpful to zero out the shape layer's position and move the path from there.