You can't have two animated characters in the same scene in CrazyTalk 7. The only way would be to add a second character on a background image but of course it would not be animated. Alternatively you could export two separate projects with one character on the right in one and one on the left and then overlay the two videos in a video editor afterwards.
However if you need multiple characters in your scenes then we recommend CrazyTalk Animator 2. This allows you to have several characters all of which can be talking. Please see the link below to find out more.
http://www.reallusion.com/crazytalk/animator/default.aspx