Hopefully you will find enough information about how to set images in your blog here.
This is an example of a post which includes a feature image specified in the front matter of the post.
The feature image spans the full-width of the page, and is shown with the title on permalink pages:
Jekyll supports the use of Markdown with inline HTML tags which makes it easier to quickly write posts with Jekyll, without having to worry too much about text formatting. A sample of the formatting follows.
