You embed an image the same way you embed other files or assets: you put the file into a folder, and then link to that file. The difference here is that the asset doesn't have a permalink, so here the file path actually matters.

Images

Put images inside the images folder in your root directory. You can create subdirectories inside this directory. Although you could use Markdown syntax for images, the HTML syntax is probably easier:

<img src="{{ "/images/jekyll.png" | prepend: site.baseurl }}">

Here's a sample:

SVG Images

You can also embed SVG graphics. Here's a sample embed:

<img src="/Manualmall/images/helpapi.svg" style="width: 650px;"/>

Here's the result:

SVG images will expand to the size of their artboard, so you can either set the artboard the right size when you create the graphic in Illustrator, or you can set an inline style that confines the size to a certain width as shown in the code above.