take you throttle assembly apart and remove the cable.
then take the cap off the top of your carby where the cable goes in, pull it all out there will be a spring and a cylinder shaped thing with a needle sticking out of it, just pull all that stuff out and remove the cable from that cylinder shaped thing.
then just put it all back together with the new cable.
remember to lube the new cable first, and if you remove your plastics and fuel tank to get to the carby it'll be much easier