If your blog is another Q2A installation with shared users, it is easy. First, copy sceditor plugin into yoursite.com/articles/qa-plugin/. Now log in as admin. Then go to yoursite.com/articles and go to admin settings, then Plugins to enable Sceditor, then go to Posting and choose the Editor.
If you use Blog plugin by Ami, things are much complicated. The blog itself is just another Q2A installation, and some of the options are grouped together, and compiled into a plugin. I can't comment because I don't use it.
