In this poem, Sara Teasdale uses a series of beautiful images to show all that life has to offer, or "sell," if we pay attention. One of the beauties life offers is the "loveliness" of music. Teasdale then uses a simile when says that "music is like a curve of gold."
A simile is a comparison that uses the words like or as. We know that "music is like a curve of gold" is a simile because of the use of the word like. Since "loveliness" is an abstract concept, Teasdale employs a simile to try to give us a concrete image to compare it to. We may not be able to visualize the loveliness of music, but we can see in our mind's eyes a beautiful curve of gold.
Poets know that emotions and ideas stay more firmly in the mind when they are linked to images that help us to remember them. Teasdale therefore goes on to use other senses than hearing to describe life's beauty. She also uses the scent of "pine trees in the rain" and the feeling of "arms that hold" to convey what life has to offer us.
What Teasdale lists as what life has to "sell" are things that can't be bought with money. When she advises we "spend" all we have for these things, she means to give them our full attention and value them.