Create a cylinder to use as a collision object.
You are now ready to apply the ClothFX modifier. Select the "Cloth" mesh and the Cylinder and apply the ClothFX modifier.
This image shows the settings that I used for this demo.
As you can see I have the gravity set to -3000. I find that it helps to make the gravity stronger to make a cloth object look heavier. Typically, when I am doing clothing I start with -2000. In this case I want the chain to look much heavier so I have a higher gravity setting.
The Thickness of the cloth object should be the width of the chain link. This is only nessesary if the chain will be colliding with itself. If not you do not need to worry about the thickness of the cloth. The stretch settings are high and the "Use Edge Springs" checkbox is clicked so that the individual faces will not stretch (if they do then the links will come apart).