Press E and Q to place portals. The code isn't perfect, so if the portals don't face, try moving around a little and shooting again. Also, you aren't able to shoot portals onto dark grey blocks. This is not a glitch, it is intentional. You are able to shoot portals through glass blocks, but not onto them. If your portal places backwards, try shooting it again, until it is oriented correctly.
I made this project when I saw another Portal project. I thought it was kinda slow and annoying to play, so I tried to make a better one. Scratch cat will not be green forever.