I have gone through the Scribus manual several times and can't find it. I'm sure it is simple :)
1. Create a new paragraph style ("Edit > Styles" or "F3").
2. In "Properties" tab, in "Distances and Alignment", you'll notice two boxes: "Space Above" and "Space Below"; change any of these two as you see fit.
3. Apply the new style to text.
Thanks Meho. That works great. I appreciate your help. :)