Alright, for lines 5-6 (A Moment, We uncertain step For newness of the night), so we are going from a well lit room to darkness and we need some time for our eyes to adjust). She calls the night "new", and to our eyes, it is. However, this isn't just a poem about how our eyes work, but how in new situations we are unsure of ourselves. She uses the figurative language, where the darkness is a metaphor for something we are not prepared for.
Lines 7-8 (Then, fit our Vision to the Dark, And meet the Road, erect)
Once we have a few moments to adjust, we can see the way. When we adjust to the unknown, we can be better prepared for the future (meet the road - erect = with confidence).
Hope it helps