Here's how I do it. In my opinion, it's not user friendly.
Insert the picture you want to enter in your gallery.
Open that photo
Above and to the right of that photo there's something that looks like a pencil - click on that icon
When that page opens go almost all the way to the bottom and click the plus sign for the contest you want to enter [IOW or POW]. That puts a little running man next to the plus sign.
Then all that's left is to click on "save Image"
If the above doesn't work, please let me know and I'll give it another try.