I think you are asking about the retrieval line. This exits the sock (at the front!), goes through the patches on your spinni and ties off at the top patch. The patches should have small loops for this purpose. It is recommended to tie a bowline at the top patch, with a 7 inch loop. The top patch should have a separate line to the top of the sail (mine does), presumably to aid total retrieval.

Cheers
Simon