I believe you may have a Furlex 100
Google "manual Furlex 100" for a PDF copy of owners manual. It will show installation procedures to be reversed.
If it were me I would take the sail down for easier working.
1) Remove Line fitting.
2) Remove Guide line bracket.
3) Remove two halfs of lower flange
4) loosen line tightening screw.
5) feedfurling line through oval hole.
6) tighten the line holding screw real, real tight.
8) assemble unit.
Make sure you take steps from preventing parts from going overboard. Perhaps laying a bedsheet against the bow pulpit to serve as net would be in order. Don't allow the Rugby player to help.