Once you are done, all you have to do is click on "Start". Img2Go will take care of the image conversion for you. All you have left to do is saving the image after it's ready.
You can also save it to Google Drive or Dropbox, of course, or edit the image even further. If you converted several files at once, you also have the possibility to download all of them in one, handy ZIP archive. Just click on the respective button.