If you are just uploading ONE picture, you can just hit "submit" afterwards. If you want to post MULITIPLE pics in the same post then you would use the "add the file" option. But even if you clicked the "add the file" button when only uploading ONE picture, it still should have posted after clicking on "submit."
Your file may just be too large. You will have to "edit" your picture and "compress" it to "web page" size. Hopefully that will work for you!