Once you click on Ideas tab, you will see at the top of the page:
Gardening ideas: new articles and tips every day! Got an idea you want to share? "Submit one here", get famous, harvest delicious acorns and thumbs, and win the admiration of your peers!
Click on "Submit one here" and these will be your options: (The first one is the simple one!)
» Easy form, like posting a thread
» Advanced form, with HTML and drag and drop image control.