not sure why so many people seem to have so much trouble replacing one file
1. download the game
2. extract the game to wherever you want to install the game
3. extract the cracked gameassembly.dll to the same folder you extracted the game to, making sure to overwrite the existing file
4. open the game, should boot and show you the authentication prompt, click authenticate and it should display the welcome message, click the button that says "Sweet!" and you're in.
I use 7zip and doing that exact process I haven't had a problem. maybe try redownloading and re-extracting the game?
EDIT: was writing this before Roshag posted. the crack is version dependent as he says. seems like every page of this thread theres somebody new having problems figuring out how to get the game working tho and idk why lol.