Marketing is usually a good idea to sell products, or services. As to the subject you might want to check the
Ultimate Guide. This reads like a 101 course type of text. Other such
guides exist to help clarify what digital marketing entails.
Be aware there is an etiquette regarding marketing online. You don't go around sending out bulk email to folks as that's called SPAMMing and considered at the least rude. The same idea of spamming applies to blogs, forums. In short people
do not like spam.
You can locate some digital marketing firms
here &
there. More of these firms are
locate-able. Would suggest letting a professional firm handle the task of digital marketing. They're likely aware of industry standards, best practices and so on.
HTH.