They, allegedly, don't ripen if they have been picked before the red pigment starts to give them a bit of a warm tinge. I have read that on the internet so it must be true. I've had pinky ones ripen OK, but not green ones. There was a film"Fried Green Tomatoes at the ???? Cafe" Calm seems to think they'd be good; I've not tried them.
You can use a jar or brown paper bag method. You will need to have two to three tomatoes along with one ripening banana to each jar or bag and seal closed. Place them in a warm area away from sunlight and regularly check them. Tomatoes will ripen within one or two weeks.