In the second stanza, the speaker talks about a girl that was really special to him. He relates a particular occasion where she visited him, and he seems a bit obsessed with her outfit. It almost seems like he's more fixated on the outfit the girl was wearing instead of, say, her looks or personality, because it's the clothing that makes her beautiful.
Line 10: The speaker recalls an occasion when a certain woman was dressed in "thin array" and looked pleasant. It's a striking image – a beautiful, scantily clad woman enters his bedroom. Who wouldn't sit right up and pay attention?
Line 11: The woman's "loose gown" fell from her shoulder. The gown falling is a rather delicate and poetic way of saying she got naked.