Incense enters the curtain and flowers speak, clearing the moon threshold.

This pair of couplets is vivid and charming with personification rhetoric. Translation is hard to convey, so we can only describe the artistic conception:

The fragrance rushes into the door/curtain, and even the flowers will think of beautiful poems (to describe it); The bright light shines on the railing, and the moon knows to snuggle up to people.