How do I set up association between two dimmers?

I know that there is a thread for this. I followed the brief instructions, but they remain very unclear. Nowhere in the wiki does it say how to actually set it up. What is Group ID? How do I determine it? What do these parameters mean:
Set to: [Set]
Currently: [View]

Basically, I want to associate the accessory dimmer Cooper Aspire RF9542-Z to the master dimmer Cooper Aspire RF9534-N. The master dimmer is the one that powers the actual lights, while the “accessory dimmer” is supposed to be associated to that master so that both dimmers can control the same lights (like a 3-way, except there no traveller wire between the two dimmers)

I tried creating GroupID=1, and I tried various options of “Set to”, but the association doesn’t work. The accessory dimmer doesn’t control the light.

Please advise.

BUMP!

Ok

I’ve managed to get this working albeit with Fibaro dimmer modules.

I have a dimmer module in master bedroom (with 2 physical switches wired into it S1 and S2) S1 controls the lights in that particular room. Triggering S2 will work with an association. I have associated it with Dimmer in daughters bedroom.

This is how mine is set up:

The dimmer (daughters room light) i want TO control is ID 3 (go to the Advanced Tab of the dimmer that you want to control and check the ALTID #)
On the device that i want to Associate it from (Master Bedroom Light) , I create a new Association (just labeled as 2)
I then select Set and choose id 3 (daughters Room light).
then i click save.

There were some configuration settings the Fibaro required:
14 = 1 as I have a toggle switch
18 = 1 to Synchronize across devices
19 = 1 as using toggle switch
17 = 0 to stop S2 trying to control the S1 channel
but i think this is device specific.

Now when i click the 2nd switch in the master bedroom, i have full control of the light in my daughters room.

Hope this helps