Basically the Saturn return is a time of greater maturity and entry into middle age. The 20s are behind you. This might be a time of greater responsibility. For example, a living-together couple might decide to marry and have a child. Someone else might shoulder more responsibilities at work.
Saturn always runs a diagnostic on our lives. If you basically get along with Saturn in your chart now, it shouldn't faze you.
There are two ways to do a planetary return chart. One is the stand-alone chart for that date and time. I actually prefer to stick to the natal chart and then show the planets for the return date arrayed around the outside, so I can better see how the return relates to the core "me". A planetary return chart is basically a kind of transit chart.
One meaning of the 12th house is people who are shut-in in some way. Something many of us have experienced lately with covid-19.