All you have to do is copy the picture (I save the ones I want to use on my desktop)
then paste it in the large box that pops up when you press,"Post." OR you can drag from your desktop and drop in the box. OR you can press the green, "selecting them" button and browse for your photo in your files. Then, you can use five words for the categories you want it to be posted in. Look under "trending" to see the categories. You can read this: https://steemit.com/introduceyourself/@photocontests/readme to find out what the catagories are for photo contests. Whew! Good Luck!