The kit should have a mandrel in it . You unscrew the tip of the mandrel and put one of the grinding wheels on it. Then you grind! You'll want eye protection when you do it, and you'll probably need pliers or a vise to hold the work. You don't want the fast-spinning thing near your fingers, and the work is likely to heat up (depending on its material). More on reddit.com

The pink ones are aluminum oxide grinding stones. They're better for use on metals, castings, welded joints, rivets, and rust. The green ones are silicone carbide grinding stones that are for stone, glass, ceramic, porcelain, gemstones, and non-ferrous metals. The shapes are for convenience. If you can't fit the bit where you need it or get the results you want, you can use a different shape. The round discs look like a set of aluminum oxide grinding wheels (the pink ones), a set of felt polishing wheels (the white ones), and maybe a set of silicone carbide grinding wheels (the greenish black ones at the top) that go on one of the mandrels. More on reddit.com

A Dremel-like rotary tool is not the tool for this job. You could do it, but you'll learn to hate yourself and the rotary tool way, way before you finish. Your least expensive solution for this, would be to buy the cheapest 4.5-inch angle grinder you can find (maybe $20, less on sale at Harbor Freight), and a couple wheels, and have at it. Despite how cheap they are, if you don't insist on pushing them until they overheat (which your rotary tool will, really quickly), they last a surprisingly long time and are a great value for the money. ... as a semi-aside, you can get a reasonably accurate comparison between how fast two different tools can remove metal, by comparing the watts or amps rating. To a first approximation, there's a direct, pretty much linear relationship between watts and metal removal rate. If your rotary tool sucks up 1/5 the power that an angle grinder does, it'll remove metal roughly 1/5th as fast. A super-cheap angle grinder might be 5.5 amps, and a good one might be twice that, and the good one will knock metal down twice as fast as the cheaper one (or remain much cooler at the same metal removal rate). More on reddit.com

Top row: Collets on the left. These fit different sized bits. Sanding drums on the right. Lots of uses, but I use them for shaping wood, plastic, and acrylic when I make knife handles, Second row from the top: Pads are for polishing. They work on metal, acrylic, plastic and the like. They mount on the threaded pointy bit in the next row. Pink and green discs are aluminum oxide grinding wheels that can be used to grind metal. Third row: Small sanding drum. This is what the small drums in the top row mount on. It looks like you're missing the bigger one. The bits include a couple mandrels on which you mount other accessories, three diamond-coated engraving bits , and two cutting bits (for drywall and maybe tile). Fourth row: A flapper sanding wheel (for wood mostly) and a bunch of cleaning and polishing bits . Fifth row: The grey stone is a dressing stone that's used to clean the other grinding bits when they get debris built up on them. Then you have more polishing pads. Sixth row: Probably polishing compounds to use with the pads. More on reddit.com