Adding images to your posts is a very important aspect of gaining a following on Steemit. An image catches the eye of a reader. In the mobile layout of the site, it is the focal point of the screen, the article title not taking up much space and being aligned the same way. Your article not having an image might be the deal breaker for a would-be reader, so it is important that one is added.
Steemit makes it easy to add images to your content. You can simply copy any image from anywhere and paste it into your article. The act of pasting will put it in the Steemit database and will assign a URL to it that will be automatically added to the page, thus rendering your image. So, again, just copy and paste and, voila, you have an image in your article. One thing to keep in mind is placement of the image.
I personally like to center my images, which can be done by putting the <center> and </center> markup tags around the image URL in your article editing field. This is especially useful when an image isn't the full width of the screen. It isn't very aesthetic to have a left-aligned image that isn't very wide. Another thing to take consideration of is where you think it is best to put the image vertically, within the content. I commonly place images above all content so that the image doesn't distract them; that being said, some content may be better illustrated through images within paragraphs, such as if you are recounting a travel trip. The main thing to note is that articles should have images whenever possible.