Search engine optimization. When potential customers do a Google search you want your business to appear on the first page of the search. Being on the second or subsequent pages means certain death. Not many people bother to look further than the first page.
To begin with, I recommend understanding that you should not take on everything at once. That is, do not try to promote 3-4 sites at once, getting mediocre results. Focus on one web project. Bring it to perfection. Take it to the top. Start earning on it. Then and only then take up the promotion of other websites, applying the experience you have already gained. I can tell you MTPremium – Official, I did audit and SEO there