You cannot set up a virtual topic without Admin's approval.
Some virtual topics can be added to by any member, others only by the person managing that topic.
You can only add your topics, the only person who can add someone else's is the person managing that particular topic.
Example: If you are making a miniature quilt, and you want it added to that topic in the virtual section, you can click to add it there. If that virtual section is set up so only a manager can add to it, PM the manager and send a like to your topic, and he/she will add it for you.
If you come across a topic that you think should be added to a virtual topic, you can PM the person who is managing that virtual topic, give them the link and they can add it.