Adding a stream to a trigger campaign

Hi, sorry if this is a repeat.  We're new users, and are in a learning mode.  We set up a smart campaign, imported a list, and sent the content to everyone on the list (thinking we were doing a batch campaign).  We now have collected some new info on a subset of those leads and want to add a new stream to send the subset.  It seems possible to add a stream, but when we schedule it nobody receives anything.  Does anyone have any advice or can you point me toward something I can read to figure this out?  All advice is appreciated.  Thanks, DC