My atomic watch is 5 minutes slow, do not know how to change the time to the correct setting

I would suspect that your watch is not picking up the radio signal to reset itself to the correct time. There are several reasons for this - the battery might be very low, or you are in a poor reception area, or you are just too far from the transmitter, or the hands need realigning. If the watch claims to pick up multiple transmitters, then be sure that it is set to the correct one. Try taking off the watch at night and placing it face-up on a window sill to give it the best chance of a signal.
I can't offer anything other than general advice as you do not give the make/model of your timepiece. Some radio-controlled watches have a facility to realign (or 'zero') the hands - again, can't be specific without more information.