When you add the image, make sure the source is a URL that everyone can access, such as http://i.imgur.com/DtYD0Yn.png

You can either use this URL with the IMG button in the forum editor, or you can write the HTML yourself. For example:

<img src="https://i.imgur.com/DtYD0Yn.png" />

Gives you this:

• This reply was modified 10 years, 3 months ago by Timtech.