Hi, I want use Google Cardboard.

Hi, in the UE 4 I can make mobile games and use Google Cardboard or only Ocullus Rift?

You can make a Cardboard app for higher end phones using the current GoogleVR plugin.
You can find the Quick start documentation here:

I have a basic blueprint for stare controls you can use here if you scroll down half way:

I get black borders around each eye, using this method. No solution so far. I’m also trying to make Nival cardboard plug-in to work, maybe you can help me?

Never heard of the Nival Cardboard Plugin.

Try using this console command:
HMD mirror mode 4

There are some more commands to try here:

All theese commands “not recognized”, using Simple HMD plug-in.
Nival plug-in is a modification of Simple HMD for cardboard use: GitHub - ludenio/UE4Cardboard: Not official UE4 plugin for very basic support of the Cardboard like VR viewers i get it to work only in 4.11.2 engine version.

I have never used this plugin so I am sorry I don’t know why console commands aren’t supported.
Have you contacted the creator of that plugin?

Have you tried using the official GoogleVR plugin?