Thy hyacinth hair, thy classic face, Thy Naiad airs have brought me home (7-8)
The speaker moves from talking about Helen's physical features ("hair," "face"), to something more like attitude or personality ("airs"). His love is about looks, but it's also about other things that are harder to quantify.
Lo! In yon brilliant window niche How statue-like I see thee stand, (11-12)
The speaker compares his love to a statue. Sometimes, when we love people, we fix an idea of them in our heads that is as rigid and unmoving as a statue. No matter how they might actually change, the person we love will always be the same.
The agate lamp within thy hand (13)
A lamp is a light. The image of Psyche holding a lamp suggests that love can illumine our lives, make things clear that were once unclear. Put another way, love is like a light in a dark world.
Ah, Psyche, from the regions which Are Holy Land! (14-15)
The fact that Psyche is from "regions which / Are Holy Land" makes her seem like an angel, something heavenly or unreal. How do you have a relationship with an angel? Um, you can't. Well, darn. Is that why the speaker says "Ah"?