If you go to the main boards page in the sidebar to the left there should be something that's says "Boards getting started" or something similar to that. If you click on it it should take you to the users guide where you can see how to format everything. However to save you the pain of looking through it all ill help you get the image in.
In order to have an image in your post the first thing you need to do is take the image you have a put it on imigur. You don't need to have an account to do this so don't worry about that. Once you have it uploaded there take the link it gives you and copy it. Now go back to the post and paste the image into it. Once the link is pasted at the end of it put [/img] so that instead of a link the image will appear. Hoped that helped.