To create a new idea simply click the "Add a new Idea button".
Next, choose the product/service that your idea is related to, enter a simple title, a detailed description and a category (if applicable). Click "Share idea" and you are done.
Once your idea is shared a Product Manager will review it and either publish it for others to vote on or will reach out to you for clarity.
You will not be able to see your idea until a Product Manager has published it.