Marketing is not a job title, nor it is a static function; it is the sum of all of the elements that represent the experience of what it feels like to do business with you, including:
Customer service - How do you answer the phone? What does that conversation sound like?
Product/Service development - What does the market need? What are the attributes of the product/service? What is the existing market environment? How do you make it? Does appearance count?
Product/Service delivery - How do you sell? What is your story? Do you provide proactive technical/specialist support? How do you capture and use learning from the marketplace?
Product/Service P&L - How do you measure success? Where is the money?
All of these activities should involve a high degree of learning while doing. You won't get it right every time, yet refuse to drive yourself crazy by letting other people continuously define how it should be done. In fact, the biggest hurdles you will ever face are the ones you have built in your own self-critical mind. So don't edit yourself or hold yourself back.
Keep nimble and mobile by reading, a lot. Read about what other people have done, process and filter the information. See inside the mind of a marketer from an earlier post. Remember that failure is only a temporary condition.