Big thank you to smirnoff for writing this for us!
Go to: imgur.com
You'll see this:
You can browse for the image file on your computer, or drag and drop the file directly into the screen above.
Once uploaded you'll see your image on screen. Right-click it and select "copy image location"
Then in your forum post paste the copied URL between some image tags.
Like this! [img]
And it will show your image.
Use width and height parameters in your image tags to scale the size of your image.[img width=100]