To get them from G+, the easiest way is to navigate to the one you like on your phone in the app, tap on the post so you get the picture fullscreen, then use the menu to download/save the image.
Then, in the app for the watchface, you simply choose custom and then navigate to where the image downloaded to. I'll go into more detail if that overview of how to do it doesn't help anybody, but it's really as simple as downloading them and setting them, as long as the person who created it did their part right.
Then, in the app for the watchface, you simply choose custom and then navigate to where the image downloaded to. I'll go into more detail if that overview of how to do it doesn't help anybody, but it's really as simple as downloading them and setting them, as long as the person who created it did their part right.