I know this is probably a stupid question, but as I just hit LC1 on my tac officer I'm rather curious.
I notice in my ship assignments menu that I have one "lieutenant science officer" slot, and then 3 slots for ensign officers.

My question is - how do I get lieutenant slots for my other types of BO's?

The officer rank slots (AKA consoles) are granted by your starship class. It's part of the gameplay balance.

This is a good resource to see what kinds of weapons / consoles each ship class has:

http://suricatasblog.files.wordpress...tierchart2.png