How To Add Column To DWT Created Using CSS Sculptor

I created a two column template within Dreamweaver using CSS Sculptor but did not save it as a preset and have subsequently made several modifications to it anyway. However, I now want to add another (right-sidebar) column to this template.

Unfortunately, I have not been able to figure out a way of getting CSS Sculptor to recognize this template. Even if I resaved it as an HTML file, I'm not sure there is a way the CSS Sculptor can recognize it. At least, I've not figured out a way of doing this using the wizard.

I don't want to manually change the code but want to use CSS Sculptor to do this. I've tried the manual approach after viewing the WA online tutorial (which is nice [Mark Fletcher, you rule!!]), but have had problems probably due to my inexperience at CSS coding. Hence my desire to use CSS Sculptor directly (after several hours of trying to manually do this).

Therefore, how can I use CSS Sculptor to add a third column to my template that was created via CSS Sculptor but not previously saved as a Preset?