Setup some portals to look something like this screenshot:
Then jump into the top portal (in this case the blue portal), and you should be under bottom (or orange) portal.
You can also fall through portals some times if you have enough downwards speed.
Setup some portals to look something like this screenshot: Then jump into the top portal (in this case the blue portal), and you should be under bottom (or orange) portal.
You can also fall through portals some times if you have enough downwards speed.