Before importing rows and columns for data form definitions, create the data form by setting up dimensions on the row, column, page and POV, depending on your requirements. Typically you define column layout when defining data forms and use ImportFormDefinition to import only rows. The resulting data form looks like the data form definition.
The rows imported from the data file are based on members specified on the data form and import options, determining which data is imported. See ImportFormDefinition Examples.