To do this in Didger 5:

1. Click File | Import, select the image and click Open.
2. The Assign Coordinate System dialog will appear. Set the correct projection parameters and click OK. The image will import in the specified projection. You can now export to a GeoTIFF.

If the image file is already imported into the project, follow these steps:

1. Select the image and click Image | Image Registration and Warping.
2. Toggle the Specify radio button, and click the Coordinate System button.
3. Specify the projection parameters and click OK.
4. Click OK. Now the image has a projection and you can export to a GeoTIFF.

To do this in Didger 4:

1. Click File | Import, select the image and click Open.
2. When asked to specify the Georeference Sources, choose ESRI World file and click OK. 
3. The Specify Image Projection dialog will appear. Set the correct projection parameters and click OK. The image will import in the specified projection. You can now export to a GeoTIFF.

If the image file is already imported into the project, follow these steps:

1. Select the image and go to Image | Image Registration and Warping.
2. Go to the Options tab, toggle the Specify radio button, and click the Coordinate System button.
3. Specify the projection parameters and click OK
4. Click OK. Now the image has a projection and you can export to a GeoTIFF.

To do this in Didger 3:

1. Import the file into a raster project, using the georeference information from the ESRI World File.
2. Go to Image | Calibrate Image and specify the projection parameters. Click Next until you finish the calibration process without changing anything else.
3. Go to File | Export and export the file as a TIFF file saving the spatial reference information in GeoTIFF Format. 

See Also:
How Do I Change The Projection Of An Image Georeferenced With An ESRI World File (.TFW) Using Didger?

Updated August 20, 2018