Here it is - that stupid NooB question....

[tlangston28]

There must be an obvious answer to this question, but I can't seem to find an answer to this on my own.

I'm learning the game using "Interruption" from BotB. The scenario lists "1xCapt, 2xLt", but there are several Captains and Lts available, for both sides, all with differing morale levels.

How do I know which ones to use?

No problem. The leader selection process is random and is mentioned in the rules: 6.1 Leader Selection. Basically, it is a random selection process. There is also the Impartial Leader Selector tool here in the Player Tools section.