Sounds like these are custom  forms, so you're doing the right thing by using
Designer; are you saying it wouldn't detect the fields? You'll need to
refresh SPD's view of the datasource, which usually means closing and
re-opening the environment (this is the only foolproof way that I've found).

I wasn't even sure what controls to use to add them correctly. I found a thread
that suggested going to:

Toolbox - sharepoint  controls - data  view controls

so i added the data view dropdownlist and selected the data column i wanted and
changed the format to list  form field  - that worked.