When you do this command, wait for the machine to generate. Then throw down a bow, iron block, and ender pearl in the same spot. Then, pick up the "Portal Gun". Now shoot an arrow out of it in front of you and then shoot another arrow where you want to go. Go into the portal in front of you and come out of the other one! You can also go back through it after this. Just drop the gun to make the portals disappear.