Upload your images to ImgBB website and then copy the HTML code HTML full linked and paste it into the topic you’ve created for it.
You do not need to have an account to use ImgBB site. See screenshots below. It may take a bit of time for your image to appear once you've copied and pasted the HTML code into your forum post. Check back in an hour or so!
And copy/paste the link onto your post on the Forum. Your link will start with <a and end with a>