You can use the "Share with others" button in your Curtains Config Windows -> Edit mode.
Press the "upload to Wincustomize.com" should:
1) Curtains will create your xxxxx.CurtainsStyle and save it into a folder for you to upload.
2) Opened up Wincustomize.com Curtains upload page in your browser. Filled up the boxes and choose the drop down menu. Upload the preview image and your curtains file. Press Submit and your Curtains style will be review by Wincustomize.com Admin. And should be release to public if there is no issue with it soon after.
Stardock Community Assistant.