It all depends ...
Where ? Somewhere different each time if you don't want badly irritated skin. I found that upper arm works well. Slightly different place each time, alternate arms. I tried putting them on my chest and I swear it caused pains and heart racing, possibly that was coincidental, but it happened a few times. They will fall off if you swim or use a sauna.
How long do you keep it on - some patches are 24 hour so you don't wake up with a craving, others are for daytime only. Depends on you and how bad your addiction is. I can't sleep with them on.
Use them every day, but use the lowest dose that works for you. They can cause overstimulation. The strong ones are STRONG. Like disco pill strong. I start talking with the spirits after a few days on the strong ones. Be careful.
They often don't work for people because the craving seems to be for more than just nicotine. Either attachment to smoke, or maybe one or more of the other 4 thousand chemicals in cigarettes.
Main advice - do not give in to the urge to smoke while using them. Remove the patch if you are going to crack. Otherwise your addiction gets stronger.
Wash the skin when you remove them if you have sensitive skin.