Hi
To insert an image, you need to have the URL of where the image is located (you can't physically insert an image into a post). Assuming you use image tags, the image will be displayed in the post (rather than just a link to the image being provided).
You need therefore to either upload the image to your own website and provide a link to it, or use one of the many freely available image hosting sites and provide a link to this.
However, if it is simply a table of your data that you want to post, and you are using Internet Explorer as your browser, then the easiest solution would be to simply copy & paste the range required from Excel into your reply.