Before you continue reading, it is assumed that you have your Philips HUE Bridge installed and working with some lights, and it has a fixed IP Address that you know. Also, the bridge must connected to the same local network (same router or Wi-Fi) than the computer running Rocrail. If not, you can check the previous post here.
The first thing you have to do in your track plan is to open the Rocrail Properties under the File menu and add a new command station of type "HUE":
In hostname field put the IP address of your HUE bridge, and leave the User ID blank for the moment. This is explained also in the wiki of Rocrail: https://wiki.rocrail.net/doku.php?id=philips:hue-en
Next step is to create in the HUE bridge a user name to allow Rocrail to access to it and manage the lights, but for that Rocrail has implemented a special functionality. Go the the tab of decoder programming, write in the IID field the name of the newly created controller and press the PT button. This will get a new user from the HUE bridge and the User ID field of the image above will be automatically filled in. At the time of writing this post the instructions of Rocrail were not updated, so be careful if you try to follow the instructions from here.
Basically, you have to select Weather under Tables menus and write the name of your recently created lights in the Outputs field (comma separated). I suggest you to use the "Colour table" and load one of the profiles already included in rocrail specially for HUE lights. Try to change some parameters to set the illumination you like, and test also the Theme tab where you can create storm effects if you have a white HUE lamp also linked to the bridge for lightning effects. I hope you enjoy it!!