Any fixture weighing more than 50 pounds requires support seperate fromthe electrical box unless the box is lister for support of more than 50 pounds.

That is the hanging hardware not a mounting bracket.

The mounting bracket is what attaches to the structure to hang the fixture from.

An electrical supply house should have (or can order) the other parts you need.

You will likely need to open up the ceiling to mount cross bracing between the joists to then hold the hardware.

Just remember that nails into wood, and even screws, should NOT be loaded in withdrawal (tension).

If you fasten the cross bracing it needs to be done so the fasteners are loaded in shear.

IT is very important to use the propor type of mounting bracket when installing a heavy chandelier. You don't want you expensive investment to come crashing to the floor.

Here is a link that might be useful: lighting

The link was not useful

It should be removed - it's a sales tactic