You don't upload images to the forum. You upload to an image hosting website, like imgur.com and put here the link, either with the Insert Image button from the forum, either with "get share links -> bbcode" from imgur.
As an additional info, newbies cannot post images (you can, but they won't be visible) [exception: copper member], hence until one ranks up he/she has time to learn.
This is serious meaning I have to rank up to copper member before I will be able to post image here?