If you would like to add a Data Transformation grid that you have already created as an Organisation Transformation grid, you will first need to Export that grid out of your template. When you export Data Transformations directly from a template, they will be saved as a .xml file. (To learn more about Import/Export of Data Transformation grids, see this section of our User Guide).
You will then need to open the Manage Organisation Transformations section of Importacular.
Next, you will need to proceed as though you are creating a new Organisation Transformation grid. You will click on the green circle with the white plus sign/cross and select a Field Type/Code table as necessary (see this knowledgebase on adding an Organisation Transformation grid).
Once you reach the screen where you would build the transformation grid, you will then Import your .xml file. Use the "Standard Import" option (circle in red below) to import your .xml file.
To watch a demo of this process, see this video.