How do I hook up a 24v transformer to a standard outlet

I would mount the x-former in a 2"x4" metal box with blank cover. Use a decent extension cord and and run that into the box secured with a Romex connector. wire nut the white and black wires to the appropriate wires for the x-former primarary coil for 120 volts a/c. Secure the green ground wire from the cord to the box with a screw. Run the secondary wires out the opposite side of the box and secured with another Romex connector.