I'll give this a try, though if you can post a few more pics it would help. Specifically, ones showing any & all blocks, sheaves, & exit plates, where lines can enter or exit the boom. Especially on the top of the boom at it's aft end.
Most likely the smaller blocks in the picture are for a cascade
purchase system for your
outhaul. So that it's pulling
power can be doubled each time it goes through one of them. And by smaller, I'm referring to the
Harken cheek blocks on the inside of the boom in the picture.
The sheaves which are barely visible in the pic, which are the aft most ones in the image, are probably the ones to be used with your reefing lines. And there should be a way to run lines into them from the top of the boom.
The reefing lines will start by being tied around the boom, run through the clew reefing cringles, then back down to the boom & through those sheaves. From there they'll go forward to up by the gooseneck, & either to a
winch there, or through sheaves at the gooseneck, & down to the
deck where there will be a set of blocks. They'll take a 90 deg turn through these blocks, & finally, run back to the
cockpit. Where there will be a
winch for them, along with a set of
cleats or jammers.
One easy way to lead the lines is to remove the boom, stand it on end, & put a leader line through each sheave at the boom's aft end. Then running each leader down to the sheave at the gooseneck.
The other option is to
work with the boom horizontally, & to use a piece of #10 awg wire to snake each line through the boom. Running each through it's set of sheaves, respectively. You'll need a piece of coat hanger wire or similar for
fishing out the leader lines in some places.
Regardless of how you install each line in the boom, you'll want to have a reeving splice on it's end so that it's easy to pull through the boom & over/through every sheave. And they're something that you'll want on the end of each reefing line &
halyard, as they let you install any line or
halyard in 3 min. or less. So they're more than worth the 5 min. that it takes to add them to each line/halyard.
If you do a search under my user name & the words reefing, boom, or reeving splice, you'll come up with a lot more info on all of these topics. As I've posted on them almost daily, a good 5-7 times in the last week alone. So there should be sufficent info for you to sort this out via them, & the above instructions. But also take a look at the various system
installation diagrams on Harken's website. Specifically, those on reefing lines, & outhauls. Starting here
http://www.harken.com/systems/