<img src="http://website.com/image.jpg" width="x" height="y">
Obviously, replace http://website.com/image.jpg with the URL of the image, wherever you've uploaded it; x is the width of the image and y is the height of the image, both in pixels. You can get the width and height values by right-clicking on an image and viewing Properties.
Or, to provide accessibility for people with sight or display issues, put a description in alt text:
<img src="http://website.com/image.jpg" width="x" height="y" alt="DESCRIPTION GOES HERE.">
The width, height and alt tags are optional but are strongly recommended.
And keep in mind that's SRC, short for SOURCE. One of the most common ways people fail at this is by typing 'scr=""' instead of 'src=""'.
The next time I do an image-related meme, I think I'll include instructions such as these just in case.