>>> which gensig > 'gensig' not found. > > We are 3 user and we are all experiencing the same issue, we had to > install the R2012a to use gensing. Unfortunately I am a completely new > user and I really don't know how to check if the toolbox is installed, > can you please explain?
That pretty much proves it isn't (at least correctly).
You'll have to find the distribution CD (or talk to the system admin if the system is under admin control or your prof if it's a uni system or the like).