One of the easiest ways to provide your photo to be embedded into a post is to upload it onto an image hosting site such as Photobucket, Flickr, etc. That should be pretty straight forward, and the individual sites will give instructions on how to get your photos uploaded to their site when you sign up.

Once your picture has been uploaded, find its image location address (URL) by right clicking on the image and copying the image location. Some sites may even provide the appropriate HTML code in a text box below the photo for your convenience. It will be the one that begins with a href=...

Let's say, as an example, that the address of the picture you want to post is http://somepicturesite.com/yourpicture.jpg

To embed the picture into a post, use the command:
img src="http://somepicturesite.com/yourpicture.jpg">;
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If your picture is too large to fit nicely into the text page, you can add a width attribute.

The command with the width attribute would look something like:
img src="http://somepicturesite.com/yourpicture.jpg"; width=600>
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Another option is to use a text link which might be beneficial to people on slow connections.

To do this, use the command:
a href="http://somepicturesite.com/yourpicture.jpg">your text goes here/a>
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Note that I had to use special characters to get the commands above to show up here without turning into pictures, but you can use them as shown (with the correct image web address, of course).