When you're available and ready to receive trip requests from passengers, slide the bar at the top of the screen to go 'Free'.
When a job comes through, you will see the pick-up address on the offer card and can click 'Accept' at the bottom of the screen to take the job. If you do not wish to take the job, then there is no need to click anything; the job offer will disappear after a few seconds if no action is taken.
If your app is set to 'You're busy' you will not be able to receive any job requests,