First of all make sure that there is a key bound for the developer console. To do this open the game and go to:

options>bindings>miscellaneous>developer console

if there is a key bound and you still cant open the console, keep reading ahead.

In this case, navigate to the game in your steam library then do the following steps:

right click on the game>properties>general> type "-console" under the launch options.



after doing this just x out of this window and launch your game, and now pressing the tilde key should open the console!