Start with looking. Ekphrasis is really about looking. A few words of description can get you into the art.
2. Write a poem from the point of view of someone or something in the art.
3. Describe the painting as if it were a dream you were having.
4. Write about the painting as if you could step into it and be part of it.
5. You can make up a story from looking at the painting. It need not have anything to do with the narrative