Jitter - the current schedule is on their website. www.knutsfordexpress.com
Each day of the week is a different schedule. I traveled going on a Thursday. Mon thru Friday the bus leaves Negril 11:40 am and 3:15 pm (but schedule changes so you will need to ck with your trip details.)

Kingston terminal is 18 Dominica Drive which is not far from Pegasus Hotel, Emancipation Park, etc. to give you a reference point. Hope that helps. more info on their site