I can see other people attaching images but the only way I see is to use the icon next to YouTube icon which demands a URL so how do I insert an image from my C: drive ? I tried using Chrome and Firefox
It is not an easily found bit of UI. I can see it in preview mode and edit mode.
I thought at one point one of the menu options allowed you to do that.
I don't know how to get pictures to display rather than just be attachments. Via the insert an image URL presumably.
According to the SimpleMachines (link in page footer) documentation, specifically the bulletin board codes page (https://wiki.simplemachines.org/smf/Alphabetical_list_of_all_bulletin_board_codes) it looks like you should use the [img] tag.
So...
[img]https://news.classicindustries.com/hs-fs/hubfs/1934Fordtruckfront.png?width=1000&name=1934Fordtruckfront.png[/img]
...looks like...
(https://news.classicindustries.com/hs-fs/hubfs/1934Fordtruckfront.png?width=1000&name=1934Fordtruckfront.png)
So, to insert your image from your hard drive, upload it to an image service like imageshack or photobucket, or even your own web site.
There's a feature available to allow users to upload images to a SimpleMachines site, but I'm sure the site owner wants to keep the forum operating for information sharing about Cognos, not a repository for the world's pictures.