It sounds like the usual two-line reefing system.
1. release your boomvang from its
cleat
2. harden the aft (clew) reefline that should go from a tie on one side of the boom, through the aft grommet on the sail, into a pulley on the otherside of the boom, and then to a
cleat.
cleat it off.
the rear (aft) end of the boom will now be cocked upwards at a crazy angle. don''t worry about that, you''re not done.
3. ease the main halyard so the front edge of the sail (luff) slides down the mast slot so the forward grommet on the reef point is even with the boom. There should be a
line that again passes from a tieoff on one side of the Mast, through that forward grommet, to a
cleat on the otherside of the mast. Harden and
cleat.
4. tighten up the main halyard again and
cleat it off.
5. tighten up the boomvang.
6. Those extra grommets in the middle of the sail along the reefline: pass short ties through them and tie them off around the boom with (of course) reef knots.
Practice this at the dock with no wind until it''s orderly and fast, because when you have to do this, it''s usually blowing.