If you are talking about taking the path an object travels along and changing it from a curve to a right angle then open the object attributes, go to the animation tab and turn on show handles. With these you can change the angles, etc using key combos. If you are really interested in Bryce then get Real World Bryce 4 (works for 5 too). This book is the Bryce bible and goes into detail of how things works. It's 1000 pages of goodness. :)