Here's a piccy if my old fazer with my home built oiler. At the rear of the engine you can see a black pump bottle with clear pipe coming off it. That goes into a 2x wider piece of tubing open to atmosphere, then sleeved down into normal feed tubing.
At the back wheel was the feed tubing sleeved down into a wd40 straw and exiting on the sprocket.

To use it, you give it a couple of pumps to get the oil into the wider piece of tubing before you set off, and let the flow commence, exactly the same as a loobman, but free!