There are two basic ways to upload an image to the forum, depending on whether the image is a screenshot, or saved to your computer.
For a saved image:
The easiest way is to use the image uploader here.
Here you can choose the file you want to use, and upload it
The next screen will provide a code to copy and paste directly into your forum post
be sure to copy all the brackets!
From a screenshot:
If your image is produced using Lightshot or other screenshot app, the process is a little more complex.
Take your screenshot, and OPEN it, rather than copy the screenshot link provided.
Then right click on the image in the browser, and choose Copy image address from the menu.
On your forum post, click the Insert Image button above the text box
This will open a window, in which you can paste the Image address you just copied. Using the screenshot address (eg prntscrn....) will result in your image not showing in the post.
Press ok, and you are ready to go