Hello CowlessTheEpic, There are multiple ways to post a screenshot on the forums. If you have a picture saved as a file, the "upload a file" button should be under your message when you are creating it. If you have an app such as Gyazo, you can click the image icon and place the link in it and it will show up. If you were asking how to take a screenshot, you can press fn + f2 in minecraft and find your picture from the screenshots folder in your .minecraft. I hope this helps! If you have any other questions feel free to message me on discord or on the forums!