You will need to submit a .csv file containing your predictions. The csv file should look like:

filename,label
domestic_cat_s_000907.png, 5
hydrofoil_s_000078.png, 8
...
convertible_s_002525.png, 1
broodmare_s_000763.png, 7

There should be 10000 predictions in total. Please check that your labels are numbers, and not wrapped in brackets eg. 1 and not [1]