Training your cat to use the harness and leash :

Harness training can be taught at any age!  It is easier when they are younger because the kitten is too worried about playing than what is around his body. While an older cat is more stuck in their ways of being free and nothing around their chest. Most cats will find the harness uncomfortable at first, but the more you put it on your cat, the more your cat will get used to the harness. Letting your cat walk around inside the house with his harness on for a few weeks before you try to take them outside for the first day of wearing the harness.  It will take adult cats a little longer to get comfortable wearing a harness if they have never had one on them.  If your cat flops over and refuses to get up after putting the harness on, let him lay there. If he likes treats, try to offer him one to where he must move to get the treat. If your cat likes toys, try to get him up to play. If everything fails, just walk away and ignore him. Curiosity will get him up and walking around.  Let him wear the harness for a while to get used to it.  Put the harness on him several days in a row, so he can get used to how it feels and comfortable with you putting it on him.