Now that you have found a theme you wish to use, go ahead and copy the entire text box contents from above like shown in the diagram below.
Once you have copied your theme, open SwiftKit and navigate to View > Settings.
Click the Themes tab in Settings and then the Import button(circled red in the diagram below). Now you will want to right click paste or press CTRL + V on your keyboard in the text box that appeared after you pressed import. Once you have done this you can click the Save button(circled green in the diagram below).
Your new theme should now appear in your list of other themes. If you wish to use the new theme you just imported select it from the list and press the Set Theme button.