Posting an image is pretty straight forward. The most complicated part is getting the image that you want to use in your post uploaded. The image file needs to be stored (hosted)on a server. I store my images on the server that hosts my website, so its easy for me. There are other hosts like image shack that will do it too.
You can have a practice at posting an image by using an existing "online" image. If you right click most images you can see their "properties". If you copy the location of that file, you can then add it to a post.
Like this..............
The text I used to include that image looked like this............
The image location can be found by right clicking the UKAT logo & selecting "properties" Like this..............
Why not have a practice by creating & previewing a post, without actually posting it. You can see how easy it is.