Add new theme to the map: Choose the option Add new theme to the map and enter a name for the theme (ex. population change). It is possible to load the wizard settings with the load settings from xml file option if you have already created thematic maps with the Thematic Map Wizard. The xml file can be chosen with the ... button. A map can have more than one theme (ex. choropleths + proportional symbols). The next button is only active if the theme name is not empty. Modify an existing theme: This option should be used if you want to change the settings of an existing theme in your map. Visit the OCAD Wiki for more information.