Posting images so that they are shown in full size is very easy when you follow these few steps.
1) Sign up at imgur.com
2) When you are logged in go to the "images" page

3) Click "Add Images"

4) When you have the image on your PC browse the image or drag it into the window, when the image is online paste the image URL there

5) Click on the image you have uploaded and copy the BBCode

6) Paste the BBCode exactly the way it is in your post

That´s all.
I know that there other ways as well, for example with browser extensions, but this is probably the easiest way because you get the "ready to post" code already without additional steps.
exactly what I was searching for. Before finding this, Ending up going into developer tools and sussed out the images were from Imgur so I signed up
but I used the direct link instead with the img html code
hehe
helpful.