I have a nissan micra s 2003 model does any one know how i can program a new key fob in.

yes. hehe.
make sure all the doors are unlocked. turn the ignition switch from OFF to ON 6 times within 10 seconds(make sure you stop in the off postion). the hazard lamps will flash twice. hold down the top button and press the other button 3 times, release the buttons, the hazards should flash once, key fob now programmed.
if you have another key fob, again press and hold the top button and press the bottom button 3 times. hazards flash once.
when finished programing the fobs, turn ignition on. hazards flash twice. all done
if no good repeat and try the buttons the other way around. ( there are different type remotes) if nogood read my posts in primera/g20 forum