Do you have it on a web site somewhere? if so click the yellow box in the toolbar above - the one that says "Insert image" when you hover over it - and enter the URL of the picture.
if you don't - I suggest using a site like ""
PicOodle! - Image Sharing"" - just use the bit on the right "Upload an image" - find the image on your PC. Upload it and copy the URL (the one called "
Direct link to image URL of image") it gives you into the Yellow box above.
Hey presto.