in case your keyboard configuration is different load the game and select options from there you can see a tab that says keyboard select that and at the bottom is a button that says advance click that. This will bring up a screen that allows you to checkmark - fast weapon change and console, the console option has to be selected to be able to open the console in game. After this is checkmarked click on the apply tab when the screen comes back up with keyboard selected scroll to the very bottom of the keyboard setting here you will see the key to hit to open the console when in game.
hope this helps.