This is ONE way to add photos to your post:
If you want to use the site's album (images tend to be smaller than hosting site's size, but can be full sized if you remove the pixel limitation, -600x360)
1.) Login
2.) Go to My Account (may have hit Home button first) and mouse down to Album.
3.) Choose Upload Picture (navigate to photo you've given a sensible name to), be sure to then hit Upload.
4.) Go back to Album, click on thumbnail to open full size image. Right click (Windows); Control Click (Mac) and select "copy image location" (its URL).
5.) Return to your reply window in the thread and click on the IMG button at the top of the compose window.
7.) Paste the image location into the window and click OK.
OR, using a third party site:
Once your photos are on a photo hosting site (such as Imgur.com; Photobucket; Postimage; Dropbox, etc.), or on virtually any site, select the full image, then Control-click (Mac) or Right-click (Windows) on the image itself, then choose copy image location. Now paste that URL (the full web address, which should end in .jpg) into the IMG box in the reply window of the thread you're posting to.