DDS is a file format created by Microsoft for use in their Direct X SDK (Software Development Kit.) Direct X provides a library to standardise and ease the development of 3D applications, such as games. GIMP is a free image manipulation software similar to Photoshop. GIMP cannot create or open DDS files by default. You need the gimp-DDS plugin to do so.
Close GIMP if you have it open.
Go to the Gimp-DDS plug in website.
Click on the "Gimp-dds-win32-2.0.9.zip" link under the "Featured" section on the left of the page.
Save the file to your desktop.
Go to the "Start" menu and select "Computer."
Navigate to "Local Disk C:" then "Program Files" or Program Files X86" if you have a 64 bits operating system.
Go to "GIMP-2.0," then "lib," then "gimp," then "2.0," and finally "plug-ins."
Double click on the " gimp-dds-win32-2.0.9.zip" file you downloaded and drag and drop the "dds.exe" file to the "plug-ins" folder.
Reopen GIMP to be able to open DDS files.