It's a little tricky, Pie lady. Here's a link to a prior discussion. More help with posting photos, please
With the changes in Flickr, that may no longer be current. Here's how I do it.
1) Go to "view all sizes" (under "Actions")
2) Open the small or medium (500) size
3) Right click and go down to "View image info" and left click
4) A page of gobbedly gook will open up but one part will be highlighted (it will end in jpeg). Copy that part.
5) Take the part you've copied and past it between the Img tags in your posting.
Seems complicated, but really not too bad.