Check w/your local SPCA or equivalent first. They often have traps you can borrow. When I trapped ferals, the drop-off time for neutering was around 8am, so I had to attempt to trap between 6:30 and 7:30am. Make sure you have a towel to cover the trap. I like to hover within view of the trap

I've never trapped ferals with injuries, so I don't know what protocol is there, but you might need to take the feral "home" with you after treatment and keep it in the trap in a safe place (like a garage or bathroom). You'll need to release the feral where it came from afterwards.