Your supposed to be watching for Frequency and Phase problems. As to specifics of how a particular software application might work, you would need to consult your documentation (Or give more specifics). The goal of the Phase scope is to show Left/Right Phase cancellation, which could cause a thin sound, and also cause Mono-playback incompatibilities. Frequency analysis, is most often used to double check a mix graphically, when your monitoring setup is less than ideal (Which it most often is in a home based setup). They won't necassarily make a better mix by themselves, but are 2 additional tools to help you make informed decisions that should result in better mixes. Remember they can be used anywhere in the mix chain too, not just on final mixes.
