Go to the
General: Regions screen and simply add a second region. Regions are really just an extra dimension in your analysis (or an extra loop in the calculations). Thereafter, the Regions screen will be accessible from the main toolbar.
Tip: I recommend setting all regions to inherit their expressions from one "base" region as shown below. That way, you can specify all your default expressions for one region and you will only need to enter additional data and expressions in cases where values differ by region. In some cases, I even like to make a dummy non-calculating "template" region that just holds default expressions, and I then enter regionally varying data for each real region.