Lol! That's laughable. A number of professional teams' photographers use Nikon cameras for sport action. In all honesty, unless it's video (and even then things are changing), there's not that many differences between the big two on performance.
That being said, you should be able to find attach buttons on your post screen. From there, you can point which file you want to upload. If memory serves me well, it's the one with the painting of a house looking button.