Still not sure what you mean. I'm wondering if you're from a site like Helium, where you have to write to an existing topic. That doesn't apply here - you can write a Hub on any subject you like! You will be asked to put it in a category but an exact fit is not really all that important - it's mainly an internal HubPages thing. You can create your own Groups to suit yourself as well, which will link your Hubs together for your readers.