The Image | Warp Image command in Didger 3 is only available in raster projects where the image has been calibrated with linear axes, and no objects have yet been digitized on the image.
Make sure you have imported the image into a raster project and go to Image | Calibrate Image. Make sure your image is calibrated with linear axes (not logarithmic). If there are any digitized objects on the image, delete them prior to using this command.
Updated March 20, 2014