You need to find the Journal to make things really work in the game.
To activate the Mirror and the Inventory simply move the mouse to the Right Side of the Screen and you will see an icon of a mirror (little goldish square), or Scroll icon.
The mirror is upper right, the scroll is a little lower to the right. Here is an image of them opened.
Also see this thread
for hints and tips. It also has the keyboard short cuts listed.
Good luck, and keep at it. It is a very fun game, and a real challenge at times.