When you are on the post a reply page down just below the box where you type your text in is a link called "Add Attachment". You click on that which causes a new window to pop up with a "browse" button. Click on it and find the file you want to upload and click "Upload File" Once you have clicked it wait and don't click it again you don't get a progress bar or anything to tell you how to to being done it is so just wait and a new screen will appear in the same window with "Note: Click here to display this image on your message." Click that and the window will close and the text required for posting the image will then be in your post. Then just continue to post like you would any other time.
If I have a picture on my computer and i want to put it on a post, can I do that?