Adding An Extra Camera

i currently have the swann dvr8-1400 with 4 pro-530 cameras and im looking to add an HD camera but not sure what one will work with my system also need to setup being able to watch from pc and on smartphone away from the house cheers guys

have a read here m8 https://www.digitalworldz.co.uk/linux-section-480/435678-old-pc-into-cctv.html