California

You should see "Post your images here" Followed by a selection bar for the size (press the little arrow), pick a size from the menu and then "Done". The next box is for how long you want the image to be available (I use no expiration). Then the 3rd. bar/box is to "choose your image". Tapping that will pop-up all the places you have photos. Pick where your photo is stored. Now locate the desired picture , click on it to select, press 'Done".
You should see postimage load your photo. Then copy the Direct Link and paste that in your post.