You might find the answers in the FAQ's
https://www.indianaopenwheel.com/faq.php
but there are 2 ways...
If you have a website and host the images on your own site. You can click on this image
Insert the web address in the popup window.
The image will appear like this...
The other way is to use the "Manage Attachments" button in the right side column. This uploads the images directly to the IOW server. There are limits for all members. You won't have unlimited uploads.
If you use this method the images will appear in the post like this...