[Plugin: WP About Author] Only show in specific category?

I’d like to only show the Author Box on posts in a certain category (“blog” category posts are distinguished from video posts, event posts, etc).

I figure I could add a conditional line to the effect of “if category=18 then” line, but don’t know where to add it to the php, or what it’d look like.

http://wordpress.org/extend/plugins/wp-about-author/