Navigate to the Bin32 or Bin64 folder in your installation of the CryENGINE 3 Free SDK.

Run the editor.exe application in either 32 bit or 64 bit.

Login with your CryDev account when prompted.

Once the editor is open, go to File | Open.

Browse to the Forest.cry file contained in the folder /game/levels/Singleplayer/forest/, and select Open.

The editor application will then load the example map forest for us with which to experiment.

Once the level is open, the first thing to try is to hit the shortcut Ctrl + G, or go to the Game menu, and choose Switch to Game.

Upon switching to game, you will be able to instantly play as if you had loaded the level in the launcher.exe application, as you can see in the following screenshot:

Using this feature, you are able to play the sample map the same way in the editor as you would in the launcher. This fact proves invaluable for iteration, because you can modify the majority of the game without having to restart the editor. It should be understood, however, that this is the emulated version of the game and doesn't fairly represent performance in the launcher as there is added overhead to running the Sandbox Editor and various debug modes.

To go back to editing mode, press the Escape key at any time.