Editing Ideas allows you to: change the title, change the description, or assign it to a different category. Navigate to the Ideas page, and click on the Idea. Clicking on the Idea will cause it to expand, and the settings button will be visible:
Click on edit:
This window will open, allowing you to change the settings. When you have finished be sure to click "Save":
In this window, you can change the Idea name, description, and Category.