Well. I use PS not Elements and I don't know if I can help you anyway since I typically use short cuts and am on a PC.
Using the selection tool, to paste a new element on a page I use Ctrl-A to select the element, then ctrl-C to copy the element. Then I click on my page and use Ctrl-V to paste it onto my layout. Then just move it around to put it where I want.
If that is even what you meant about adding a random element, lol.