95% of the people that responded to this question have given you the answer you need to upload image.
But if you still don't get it right, kindly Copy someone post with image and then edit it to upload your image.
Example; Go on bitcointalk, check someone post and click Quote to copy the HTML Code of the person. From there you will see the link to the users image, Delete the original link of the person by inserting your. When done copy the edited version to paste on your dashboard to upload.
That's how I learnt how to started posting image too
I think that's more confusing task because if you are going to edit someone's else image tags and inserting your link there then chances of mistake are more and you will see invalid image proxy code so the best solution is to follow the instructions above to upload the image on any image hosting site and simply copy the BBCode in your post.
If you want to make image clickable then embed it like this :
[url][img link here [/img][/url]
That's it and your image will be visible to others as well you on forum if you are not newbie on the forum.