Also, if you are trying to embed a picture from a random spot on a website things can be a little tricky. The text following the picture below, will show you how to post a picture like the one below if you are having a hard time with it.
If you cannot click on a pic and go to a blank page with only that picture, try right clicking on the photo. The picture below shows you an example. Disregard the option to view photo, as this would not be present if you could not left click the picture to view it by itself. I have highlighted Copy Image Location. Left click Copy Image location. This saves the picture's interweb location. Then all you have to do is come back to the thread that you would like to post in, go to the reply section and find the insert image button (it's right above where you type and is yellow with a gray mountain and sun). Click that and it will ask you to enter the URL. Simply right click in the text box, and select "Paste" (or simply press "Control+V" to do the same thing a fraction of a second faster). Press OK, and then preview your post so you know it looks how you want it to.
Also, another option in the picture below is Save Image As... A lot of pictures are copyright protected and will not give you this option, but if you see this you can save the image (download it) on your PC and the upload it by selecting the Attachments button (looks like a paperclip) on the "Go Advanced" message screen. Click browse, find your saved file, then click upload. Once again, click preview post to make sure your message looks how you want it to.
This is the picture I was referencing above talking about "Right Clicking":