In order to post pictures you have to have an image hosting account on a website such as photo bucket or imageshack etc....
From there you have to "import" your photo(s) from your device (in my case it an iPhone) to your image hosting account.
Once you import or upload your photo(s) to your image hosting account, it is there until you delete it.
When you go to post a picture, you need to have two tabs open on your browser: your blade forum page and your image hosting page.
On your blade forum page you will write your description etc...then you need to locate the icon in the top of the box you are typing in. It looks like a tree in a square. This will open an area to type an "image code"
Then go to your image hosting site and copy and paste the image code from the desired photo to the text box on the blade forum page, then hit save.
After hitting "save" the image code will show up as text under your description of your item you are trading. Once you select "submit thread" or "post quick reply" the text will change to an actual image.
Hope this helps, feel free to contact me if needed. There are probably easier ways but its the first way I learned.