Staad Pro

Basically I'm using Staad Pro to answer a report which is "Effect of cracking on Stiffness of RC Frames" Parametres are given L=6m H=3m B=0.3 D=0.6 at 100% there's no cracking at 20% cracking the height will be 0.2 x the 3 at 30% 0.3 x 3 etc the same for the D which is depth at 100% no cracking at 80% 0.8 x 0.6 etc main problem is Staad Pro has no cracking analysis, how do I observe/input all of this in to staad pro, anyone got a clear tutorial, also what am I exactly doing, is it a beam? or 3 beams stacked together to make a frame, like what is it, what do I click to start from start to finish would be very helpful and what am I looking for, what am Is the teacher looking to see, because in graph at the end is it bending moment?? the terminology of the program is so confusing, from nodes to supports just brain freezes me, help would be really helpful please