To get area from shapefile is available only when your project does not contain plot with grid layer (or you don't use it).
  1. Click Get area from map button


  1. Browse directories and select shapefile to get area from
  2. Click Open


  1. New window with preview of selected shapefile appears
  2. Select attribute defining individual categories of subplots (classifier)
  3. Tag those classes to be included in area calculation
  4. Total area (in ha) is being updated with (un)tagging of individual categories
  5. Click Perform and use result


  1. Total area is updated