How to catch a wild bird?

Theres some kind of robin stuck in my porch, it got in there in the middle of the night and has been there for more than a day. Im pretty sure its wing may be sprained or broken and its just got its claws wrapped arong the netting on my window with its wings partly bent strangley and i think i should take it to the vet before letting it go. The poor thing looks pretty disoriented and hasnt had foor or water for 1 1/2 days at least and it keep on pecking at the netting. The porch door is wide open but i dont think it can even fly out anyway, how can i cqtch it?