Adrian @nannyjulie
The simplest way to get a clickable link is to create a preview (small picture with text). Open the item you want to link to and then select and copy the URL (the address bar at the top of the page - see photo), then return to the forums and paste it into your reply box. Make sure you put the link on a line on its own with no leading spaces or it will not show the picture. I use a Mac so it may look a little different on a windows computer.
Alternatively if you wanted to put a large picture with a clickable link
Sarah @thedotterypotter wrote a tutorial to help put a large clickable picture on the forum - link here
https://talk.folksy.com/t/how-to-create-a-large-clickable-picture-in-your-forum-posts/15874
Hope this helps