When you are compiling a post, there are several additional options at the foot of the posting box.
click on upload attachment and browse your local files - click on the picture / file that you wish to upload. then click on the add file box. once the file has uploaded it should be listed below - giving you the option to add a comment, place inline or delete file. the place inline option should post your pic inline with the text that you are writing / your cursor position. if you don't use the place inline option the pic will appear at the foot of your post.
when you have finished composing your post - click the preiw button if you wish to view your post - press submit button when you are ready to post it to the boards