If you are unsure how to embed an image from the internet to your post, then I attempt to explain.
First it is important to know that the image must be on the internet and not your personal computer. If you wanted to have your own pictures on the internet then sites like photobucket or imageshack are amongst some bigger name companies that you can set up free accounts with.
When you do find an image that you like right click with your mouse and scroll to Properties. Then click with your left button of the mouse to bring up the Element Properties box.
Where it says Location you will see a web address (http://www.example.com/12.jpeg) Highlight this address by holding down the left button on your mouse and dragging your mouse to the right.
Then copy the address by either clicking the right button on your mouse and selecting the copy option from the drop down menu or pressing ctrl + C
In the forum you will see this image 
Press it and a box will appear. Where it says Image URL is where you paste in the address of the image you wish to use. Click ok and your image will appear in your text editor.
This is how you post an image in your messages.
NOTE: you can decrease or increase the size of the picture by holding down the left button on your mouse and dragging in or out.
A little knowledge that acts is worth infinitely more than much knowledge that is idle.