First, navigate to the event that you want to import results for. On the top right hand side, you will see a section called "Results." Mouseover that and choose the first option for "Import."
On this screen, choose the event you want to import athletes for, locate the .CSV file on your computer and click "Save."
After you import your file, you will be taken to a screen that asks you to confirm the headers of your .CSV that you imported. Label each column with the corresponding header and click "Save."