This has been asked before, please make a search.

Copy and paste characters you want to another image

you mean combinate two renders in one image? i can give you some steps
1º get a editing program
2º Go to balto source galleries and choose two images you want
3º render them both
4º paste both into the same background

if what you want todo is something like this http://www.animationsource.org [...] 7.html&numart=16653&display=18
at least this is what i did thanks to my wonderful teacher for the lesson MJW luv ya stepson^^

Well, first your going to need a program like GIMP or Photoshop.