Press "Play SteamVR Games" in RiftCat client to make sure that SteamVR driver is running. Start the game in Steam and then click "Launch" in the Elite Dangerous Launcher. Once the game launched go to Options, and then Graphics. Navigate to 3D and select either HMD (Headphones) or HMD (Speakers), whichever you are using.
If your headset is using uncommon settings expand 3D settings where you can adjust 3D Separation, and 3D Focal Distance to your liking.
Elite Dangerous has a known issue of having problems with text readability. To improve it, click the Wrench button in RiftCat Client while having your phone connected to the PC.
Expand list "Advanced Video Settings" where you will have the option to increase Render Scale which improves text readability. Note that Render Scale greatly reduces performance, so don't overdo it.
Now you are ready to play and enjoy Elite Dangerous. You can control the game the same way it's being done traditionally. You can also rotate your head to look around. Have fun in Elite Dangerous with VRidge!