You need to learn about business operations for one. A CTO (unless at a small company where CTO means head engineer) has to worry about risk of chosen solutions

You need to learn about business operations for one. A CTO (unless at a small company where CTO means head engineer) has to worry about risk of chosen solutions, governance of IT, setting strategy for how technology fits into your company's operations, emergency plans. There are a lot of good case studies and papers in Harvard Business Review that can start you thinking about these topics. I'm not sure on landing the job, but a CTO needs to think on that level, which is quite different from software development. Being familiar with the topics and able to sell yourself as a person who understands these topics will help you.