Thu Oct 09, 2014 2:02 pm
You'll see a message in the log about "so-and-so has been congratulated for his victory. New Seniority is X, and he is now promotable" (something like that, I'm recalling from memory here). When you find him, his unit card will be blinking, and the Promote icon will be active (colored in, rather than black and white).
The tooltip for the icon will inform you if you're skipping over other generals by promoting the one in question (if he's not senior enough).
The general needs to be in a stack by himself, or he needs to be the most senior general in the stack that he's in, in order for the promotion to work. Click the icon, and when the turn processes he'll be promoted. You'll see a message in the log about him being promoted, and a message about any generals that you've upset by passing them over.