1. Open itk-SNAP.
   Here is an image of the icon:
   
   
   
    
2. Click the "File" dropdown menu, then select "Open Main Image", as shown in the image below:
   
   
   
    
3. Click the "Browse" button, as shown in the image below, to locate the folder containing the ct data, and select the first .dcm file (the exact file you select does not matter - itk-SNAP will be aware of all related files in the directory when at least one file is selected to load the data).
   
   
    
4. Once a .dcm file from the ct data has been selected, click the "Open" button.
    
5. Then click the "Next" button to load the images.
    
6. You will now see a summary of the ct data like the image shown below. Click "Next".
   
   
    
7. You will now see another summary of the data like the image shown below. Click "Finish" to finally load the data into itk-SNAP.
   
   
    

Your itk-SNAP window should now show the three axes of CT image slices similar to the image below: