When you import a CSV or XML product feed to our system, the system tries to discern whether its structure fits our pre-defined import schemas. If we can't find a matching schema, this is what you will see.
At this point you need to help the system learn how your source is built. First select the element in which your products are contained and then manually combine the "Imported elements" with our "Internal elements" by simply dragging and dropping them in the "Mapped elements" section. You can see the whole process here.