You'll want to make this really tight because this is where your camera attaches. You want it tight not because it'll fall off or anything, but because putting the camera on and taking it off requires lots of turning action. If it loosens, the bolt will pivot around as will your camera making hard it to keep still. If this happens while you're filming, you'll have to stop and find a wrench. This schematic view may be a little clearer than the pictures.

Use a hammer to dent the center of the flange washer. You can do this by putting the washer across the hole of the weight, putting the head of the bolt on the hole, and hammer the bolt. You want to have the center area of the washer higher than the rim. So when you attached the mount to the camera, as shown in the right picture, the rim of the washer pushes up against the area around the bolt. This washer will distribute the force away from the single point of contact. So, the wider the washer the better. If you don't use the washer, the camera will shake a lot right at this connection as well as putting a great deal of stress on this one tiny spot that could damage your camera. So if you lose this washer, I don't recommend using this steady cam without it.

Use your fingers to tighten the wing nut on the mounting. DO NOT use a wrench. You may risk stripping the threads on your camera or breaking the tripod mount. Both are equally bad.

You'll need the barbell weight and the parts shown in the pictures below. They'll go together in the pattern shown in the next picture. The bolt goes through two washers that sandwich the weight. Then stick on the end cap, put on the lock washer, and then finally the nut. Hand tighten the parts until they are snug. This schematic view may be a little clearer than the pictures.

The lock washer deep inside the end cap will keep a grip on the nut. So, you don't have to stick pliers down there to turn it. Just turn the cap. Stick the cap in the vise shown on the bottom left. Then you can use the screwdriver to tighten the bolt, or just grab the weight and turn it. The weight should turn the bolt, and the vise will keep the cap from turning.

I like to tighten it until the outer washer starts to bend inwards. This reduces the amount the bolt sticks out - good for when you want to put it down on the base. If you do use the base as stand (not highly recommended because it's easy to knock over), you can buy rounded bolts and little rubber feet. These will make a much nicer base that won't wobble. You can tell I like to do this and I say it easy to knock over from experience. My camera still seems to work okay, though.