The advantage of hotlinking images is that you push all bandwidth costs to the image host, which saves space for your website.
NEVER hotlink from a source that you are unfamiliar with. Certain website have scripts that at best will block your ability to hotlink, and at worst will return images of the external website's choosing.
1) Right click on an image that you would like to hotlink.
2) Copy the image address. This gives you the specific image address of the photo
3) Return to your website.
4) Click on "Edit Page" on your website
5) Insert the photo by clicking "Insert Image."
6) In web address box post the "web address."