Familiarise yourself with the controllers before you get started and make sure you are comfortable with the buttons.
The following gives you an idea how the different controls on your controller are used:
Pulling the trigger performs the primary action for the tool, e.g. teleporting with the Navigator, moving something with the Grabber, etc.
Some actions distinguish how far you squeeze the trigger.
Menu (Vive), A button (Index, Oculus)
Access the Tool Menu and change tools.
Click the Menu Buttons on both controllers at the same time to go to the Asset Library.
ThumbPad (Vive, Index)
Tracks the position of your thumb and usually controls a radial menu of up to four options - left, right, top and bottom.
ThumbStick (Index, Oculus)
As the ThumbPad, usually controls a radial menu acting like a d-pad.
B button (Index, Oculus)
Usually provides a direct binding to the Inspect Menu. Vive users will find Inspect in the Grabber radial menu.
On flat UI components will open a popup menu.
Primarily used to move around the stage.
In some contexts, clicking the grip button will toggle alternative behaviour for the current action.
The grip can be an awkward button to locate, but with 1st finger on the trigger you should find it on the side of the controller under your 2nd & 3rd fingertips (Vive) and 2nd,3rd & 4th fingertips (Index).
The System Menu button is not used by FirstStage (except to wake the controllers).