Select the variables and the observations to display

To choose the variables you wish to display in the central area, you have just to tick the variables in the section Variables in the right lateral explorer (this explorer is previously present in the section Environment).

Note that by making a left click on a variable from the list (or the header of the column in the spredsheet), it is possible to Modify. This allows, for example, to modify the name of a modality or the name of the variable.