I am a CTO and most of the time you won't be doing any coding or anything technical, after all, you can always hire people to do that, train them, mentor them, and give them a quality job and a good salary.
The thing is, a CTO is a company executive and his position is to deliver results, raise company revenue, etc.
You know how to code, so you should start by looking into project management methodologies. How many developers do you have in the company? How are projects managed? If it's a small company with a guerrilla team you should look into something like Agile methologies/SCRUM. Learn how to manage the projects and employees, read a lot and do courses about it, be a technical mentor to them, but forget about doing the coding yourself.
Also, try aligning with the CEO. If it's a small company and you already is the acting-CTO, get to talk to him, suggest changes to the projects that would increase market value, or suggest incremental changes to the products that would allow the company to bill the customers a lot more.
Get to know the customers, you are not the technical guy anymore so you won't be talking to the customers users, talk to their bosses. Take them out for lunch/coffee, networking now will become a huge part of your career and you'll see yourself doing that almost all the time.
How's the customer support dept? Get to learn that too, there are hundred of support methodologies on how to make customer support more responsive and achieve better results.
Also, how's the product/project marketing going? Have coffee with the marketing manager or 3rd party marketing agency and get to know the projects they are working on so you can align the product/project, have ideas, make things work better.
Talking about privacy, how's the company security in general? Thats the no.1 worry of every CTO in 2016, from how data is secured, to how passwords and how people treat things in general. The other day I was giving a speech to hundreds of our employees on how hackers work with social elements of their lives and how important security is to their jobs.
How's the company software/hardware inventory?
Most important of all, have you defined KPIs for every project/product? Do you have a roadmap? Most of my day I spend answering emails/phone calls, having meetings and looking into a screen I developed myself with hundreds of graphs/KPIs indicators, from that I can see the general health of the company, its projects, products, deadlines, results, etc. If you are technical enough you can do that yourself... I even had a big flat screen tv installed at the office showing the KPIs all the time.
Forget technicalities now and start studying like crazy, there are hundred of videos on youtube on project management, SCRUM, agile, etc, there are thousands of content online on how to effectively manage people, how to get results, etc. There are hundreds of groups in Linkedin, where you should probably spend a lot of time now networking with executives from other companies.
Last and most important tip of all:
Forget working hours.
Executives make big money because they have other mindset. Don't go to work with an employee mindset of doing 9-5 and getting your vacation time. You are now being paid big money to forget things like working hours, you are now being paid to deliver, and if you have to work 24h to deliver something, it's your problem. , you'll see yourself answering emails at bars, having phone meetings where you're traveling abroad, etc.