Most forums will only accept photographs in .jpg file format and in fairly small file sizes. I keep all my images in the Canon RAW format and most are about 25 Megs in size, therefore they would not upload to the forum.
I start by reducing the size of my image, normally to 3" x 5" and then save it in the .jpg format, which I compress to provide an image size of less than 100K. I complete this image conversion in my Photo Editing software - Photoshop CS5.
I then go to a photo hosting website -Thewebsite I upload to iswww.use.com
Once you create an account you can upload the photographs. You then select the button "Generate HTML & Image Code". This provides you with multiple lines of code. I select the appropriate code, select copy and then paste itinto the forum's message body.
You must ensure that [img] precedes and follows the code you pasted into the message body. I then select preview and if not correct I tweak the code.
Hope this helps, if not send me a PM with the problem and I'll try to help.