You need a mandate from the business that will give you at least half a day, if not one full day per week, to learn the role. The business should also provide the means to educate and train you and others who wish to become security champions. Increasing and spreading knowledge will increase awareness and control.
You need to be a programmer, and understand code, because your job is to start looking at your application and understand its security properties. You should also know 'the tools of the trade', and how to implement them, in the most efficient way. Lastly, you must be able to identify useful metrics and instruct on how to obtain them.