Step 1: Find and download image .
Step 2: Upload picture .
Step 3: When finished uploading the page will show you your image. Right click on it and save the link location.
Step 4: Create post and use the Image button below your post window and paste (Ctrl+V for us Windows folks, Mac folks probably use an Open Apple/Closed Apple key sequence ) the URL into the window that pops up.

That's about the gist of it. If you need practice just start a thread of naked Jennifer Connely pictures and see if it works.