The way the first computer programmers told computers what to do was by learning the binary language of computers and then translating their goals directly into binary instructions by themselves.
Early programmers had to work directly in binary, which meant they were literally writing instructions in the same 1s and 0s that the computer understood. It's kind of wild to think about having to manually translate everything you want the computer to do into that low-level language without any of the shortcuts we have now.