What you will need to create one of these:
B) a really long sketch (I stitched seven A4 sketches),
and C) Download the template by clicking this.
1. Open your panoramic sketch on a jpeg file.
2. Open the above mentioned link "360template.jpg".
3. Place your panoramic sketch in the 360template.jpg file.
4. Make sure it's centred, then flatten the file.
5. Hit "Save" (not "Save As").
6. Drop image in Facebook and it will automatically detect that the file is a 360 pano image.