First after you save your image to your computer, find an image hosting website such as postimg. or imgur!
There you can upload images from your computer, and then you can get the link for the image!
Come back to the forums, and do [image] link of the image [/image] on the post and the image should pop up!
Question Answered, Thread Closed.
If you have any more questions about image posting feel free to privately message any of the sentinels from your community!