Is your WordPress hosted by WordPress (i.e. www.mysite.wordpress.com) or have you installed WordPress on your own remote Server (i.e. www.mysite.com)?
Either way, I wouldn't advise using Site Sculptor to make cosmetic changes to your page design. It would be easier (in either case) to just adjust the stylesheet(s) that apply to your site design.
If you have a WorPress hosted blog, then those changes would be made from your dashboard: Appearance > Edit CSS > CSS Stylesheet Editor.
If you have installed a WordPress blog on your own Remote server, then the stylesheets for your blog pages will be in your WorPress directory > wp-content > themes > css .
If there are any specific changes you have in mind, you could post a link to your site, and someone should be able to help you with it.