Looks like you have a good bit of the basic equipment you're going to need other than a couple if powerheads and test equipment. That light will only be useful for seeing the fish. You'll need way more light for corals after everything is setup. You'll need proper reef sand and live or dead reef ready rock.
I wouldn't rush anything just yet. You'll want to look on YouTube for videos on setting up a HOB
overflow and sump. That'll show you how that part of the equipment works. It can be tricky but it isn't all that hard. You can also look at the stickies at the top of this forum for a lot of basic info on setting up a saltwater tank.
It's a good idea to start a list of the items you're looking to buy and run it by us on the forum before you spend money on stuff. Well let you know if it will be ok to use in a reef. Stuff you'll need to start will be salt, a refractometer (to test salt levels), a powerhead (to mix salt and create water flow), RO
water, a basic saltwater test kit for ammonia, nitrate & pH (at least), a heater, and a book. I'm betting you already have water changing equipment from your freshwater tank. The sand and rock will come next.