Sail sfbay's diagram pretty much gives you all you need.
1. There are usually 2 holes in the headboard(that's the plate at the top of the sail where you afix the halyard.)One hole for the halyard connection, the other for the topmost slider/slug. There's enough room to add another slide, you can attach it with a couple wraps of cord, or maybe even find a metal or plastic shackle that'll fit. I'd just tie it on rather than spend a lot of time fitting the shackle.
2. Regarding the mainsail's forward boom connection there are usually two cringles (holes with grommets) pretty close together, the lower one is for the attachment to the boom fitting. Since I don't see a ramshead(that's what they call the hook style attachment) no big deal. Again, you can go find a single or twin hook and a fastener, or a big clevis pin.... but if it were me... I'd just tie it on the same way you'll do with the mast slider.. you can even use more of the same line.. just wrap it around 3 or 4 times and tie a slip knot. Go sailing. Okay, the upper cringle, if you have one, is for the cunningham. I leave it to you to research that... but a cunningham is a very useful sail adjustment tool. Instead of using the halyard to control tension on the main, the cunningham takes it over.. tensioning downward rather than up with the halyard.
There will be a 3rd cringle a couple feet higher, that will be at matching height with a cringle on the leech. This is your 1st reef point. Many boats will only have 2nd, even 3rd set of reef points... if yours does.... that's cool...butl you'll learn about that later... if not... no worries.
3. This brings us to your boom end set up. If you examine sf bay's illustration.. there are three sheaves, you'll see one for the outhaul's control line. one for the leech reef point, and one for the "adjustable" topping lift. This set up is pretty handy. What you'll need to do is get rid of that swollen rag of line you have now, and get some 1/4" line long enough to connect the static line topping lift, down through the block at the end then all the way forward where the outhaul emerges. Usually there's some kind of built in cleat at the front end, but it might be more convenient to route the line aft to a simple cleat mounted on the coach roof so you can control it from the cockpit. Again, closely inspect the diagram. Others will be happy to explain the function of the topping lift.
Seems like you've figured out the outhaul, that is a super important sail adjustment, it usually has some purchase configuration hidden inside, so make sure it works.
Finally. the reefing line should be set up per the diagram. It will exit the front of the boom as noted before. You'll have one line for the leech (back) and one for the luff (front). To set up the mast end you'll want to extend a line from one side of the mast, up through the reef cringle, then back down to fastening point on the other side of the mast... a simple horn cleat will work fine... this will give you 2:1 purchase to get the luff nice and tight when you reef. Look for a small eye strap a foot or so below the boom on the side of the mast... the cleat would be on the opposite side.
Okay, that's my two cents. Good luck, have fun.
