What it looks like: Your dog will nose the palm of your hand.
start with treats in your left hand in a closed fist. place your fist behind your back.
Walk backwards and when your dog is following you (keep them on a leash if it works better)
and present your fist that was behind your back, when the dog approaches your hand click and reward. The goal for this step is to have your dog nose your fist, click and reward for movement towards your hand and eventually when they nose your fist.
Once they master that step, remove the treats from your fist, still click and reward when they nose it.
then instead of making a fist have an open palm.
Then instead of presenting your hand from behind your back just walk backwards then show your palm, click and reward for nosing it.
Stop walking backwards and just present your left hand, click and reward as soon as their nose touches your hand, timing is very important.
Add in the verbal cue (name of the trick) Say touch and then present your left hand. Click and reward.
Change where you present your hand go lower go higher etc. not by much, slowly change the picture, then try with your other hand.