If you are planning to become a Digital Marketer without spending or joining its course then initially try few tasks out of many for it. The content you would like to promote or market online can be done using various social media websites viz. Facebook, LinkedIn, Twitter, Instagram, Pinterest etc.
The next one is, if you have created a brand profile in every social media and suitable website to promote the content then it would work even better. Likewise, you can do it for other brand association as well. Guest blogging works well too.
Interacting with followers or customers works beside. Developing existing content beside adding a new one matching the niche helps in Digital Marketing. One of the success of Digital Marketing is promoting or offering discount or announcing the Contest with its follow up till the end, like announcing its winners and on.
Other than these few steps, observing analytics or reports to track growth, response or ROI etc. are very important. Email Marketing, Website Management, SEO (Search Engine Optimization) and email newsletter etc. helps Digital Marketing. These are just few steps and there are many more to do it and you can learn when you begin it slowly.