how do I create areas from polygon lines?
Easy. Use Trace. In the Transform Reference, see the Transform - Geometry: Trace topic.
how do I get the surface area (e.g. in m2) of an area calculated?
Easy. Use Copy : area. In the Transform Reference, see the Transform - Geometry: Copy topic. The area option is so simple it's not illustrated (I think it should be, and have sent in a suggestion), but here's how:
1. Open the drawing or the layer in the map that's got the areas of interest.
2. In the Transform pane, choose the drawing with the areas of interest (in the screenshots the drawing is named Areas), and choose the Geom field. Double-click Copy in the list of templates. That launches the template.
3. In the Copy template, choose area as the Use option, and choose whatever units of measure you want.
If the drawing is in lat/lon (for shame!) you get a choice of arc minutes, arc seconds, radians or degrees. If the drawing is in some sensible projection (yay!) that uses linear measures, you get an enormously long list of units you can choose. Choose meters, for example, and you get areas measured in square meters.
The Measure box, by the way, lets you choose either auto (native Euclidean for linear measure projections and geodetic for lat/lon) or geodetic, to always use Vincenty formulae over the ellipsoid.
4. In the Result box, give the name of a new field that will be created in the drawing's table into which the results will be saved. It pays to name it something memorable, like "areas in square meters" or whatever.
5. Press the Transform button.
What's definitely useful about the above is how easy it is to get units of measure in whatever you want, like in square feet or square miles even if the drawing's native unit of measure is meters.