Check your local college or university for a technical writing certificate program. Look at the faculty of the program to confirm you are being taught by professionals in the field or working content writers who are familiar with the demands of the writing industry. Certificate programs can be beneficial for writers who are new to content writing or technical writing.
To explain how content marketing works, we first have to agree on a definition. Unfortunately, I might've sent myself on a fool's errand -- I went through dozens of different iterations of a content marketing definition (including the somewhat flippant "content marketing is using content for marketing") and found none of them totally satisfactory. But I hate to let perfection get in the way of progress, so let's just get something down on paper so we have a basis for discussion:
If you haven't already noticed, you're currently perusing a blog post. Blog posts live on a website and should be published regularly in order to attract new visitors. Posts should provide valuable content for your audience that makes them inclined to share posts on social media and across other websites. We recommend that blog posts be between 1,000 and 2,000 words in length, but experiment to see if your audience prefers longer or shorter reads.
You write a blog post about your infographic generator, and included a link to the tool in the post so people can try it for themselves. Let's say the visitor-to-lead conversion rate is the same on this blog post as it was in your PPC campaign -- 2%. That means if 100 people read that blog post in your first month, you'd get two leads from it. But your work is done now. And over time, that one blog post you wrote years ago will continue to generate leads over, and over, and over, every single month. And not just that blog post -- every blog post you write will do the same.
The content you create should be shared on the social networks on which you're active. (And if you're not active on any, this is one of the reasons to get started.) Moreover, Google's algorithm considers social signals as one of its most important ranking factors -- socially shared content is a vote of approval, or at the very least importance, so it makes sense Google would consider it when deciding whether a post should rank well in organic search.