You can insert images into any blog post – here are some resources to help you with that:
https://en.support.wordpress.com/images/
The images will be displayed on the single post page, like this one:
http://wp.me/p6QPOk-6
For the post excerpts on the blog page, you have two options:
1. Add a manual excerpt in the Excerpt box, OR,
2. Let the theme pull in the first portion of the post automatically.
If you choose #2, images will not be displayed in the excerpt on the blog index as any HTML in the in the excerpt is automatically stripped out.
If you opt for #1, you can include images in the Excerpt box, but you’ll need to add the code manually. You can do that by switching to HTML view and copying over the code you need into the Excerpt box, including the image code.