The rule of thumb to follow when posting a new topic, is to first select the sub-category you would like your post to appear in.
For example:
If you are wanting to post a stalking opportunity, and it relates to Triangles, first select the Triangles sub-category,
Once in the sub-category, you will then notice that the "+ New Topic" button will allow you to create and post your topic.
Once you have detailed your comments, simply select "+ Create Topic" to make your post live.
NB. If you select the Category "Chart Stalking" by accident, you will note that the "+ New Topic" button is not accessible.