To enable the dev console, go to the main menu of the game, click Options, in the keyboard tab(open by default), click Advanced, then check "Enable developer console(~)", and confirm with OK on both the advanced window and the options window, this should solve your problem.
Alternatively, you can open the console by opening the steam games list, opening the properties for Sin Episodes: Emergence, clicking "Set launch options" and typing in -console , close the dialogs, start the game, and the console will come up.
Remember though, if you close the console, the only way to bring it back up is to restart the game(if you're unable to use tilde), you can drag it out of the way and start the game, and open/close the pause menu to show/hide it.