: Open Nucleus Co-op and use the "Download Game Handlers" search to find the Black Ops 1 handler.
: For the most stable experience with modern PC hardware, many users prefer the Plutonium Project version of Black Ops 1, which includes various engine fixes and better controller support.
: This is the industry-standard tool for adding split-screen to PC games that lack it. You can find the latest version on their Official GitHub.