The smaller part, the swivel, is attached to the head of the sail. The sail should have a piece of rigging
wire sewn into the luff. Any sailmaker should be able to do that for you. The swivel is hooked onto the headstay by means of that pair of opposite facing hook things and then hauled aloft with the Jib
halyard. The system will work best if it is a two part halyard. You really need to have it tight.
The tack of the sail is attached to the top of larger piece, the drum, and the drum is attached to wherever you usually attach the tack of the sail. The drum will have a furling line
passing through the fairlead on the end of the lead arm and already wound around it. After the sail is hoisted, you pull the line
and the sail winds up. It's pretty much that simple.