Install the latest GeForce display driver available at http://www.geforce.com/drivers. This will automatically install GeForce Experience as well.
Launch GeForce Experience.
Click
Scan for games.
On the My Rig tab in GeForce Experience, confirm that your PC meets the hardware requirements for game streaming.
Log in to GeForce Experience using the Log in button on the top right corner.
A new window appears, giving you two choices: (1) log in with a new NVIDIA account that you can create from the window, or (2) log in with your Google account. You must log in with the same account you use on your SHIELD.
Press
the SHIELD button
to launch SHIELD Hub and select the “PC GAMES” tab. Log in using
the same credentials you used in GeForce Experience.
You will now see a list of supported PC games that are available to stream from your PC.
On-screen controls allow users to interact with game
dialogs to make GameStream a better experience on SHIELD. To access
GameStream on-screen controls, use a two-finger tap or long-press the
Start
button.

The on-screen controls will bring up a menu screen with three options: Keyboard, Quit, and three-dot menu.

If you need to input information into a dialog, use the Keyboard selection. If you want to quit the game, select "Quit game."
Most of the touch navigation options are straightforward. Clicking three-dot menu > Help will display the full list of available touch interactions.