Show your dog your hand.Your dog may smell, lick, etc. to figure out what you want. Wait it out without speaking. When your dog paws at your hand, click/praise, open your hand, and offer the treat.
Try this multiple times until your dog always paws at your hand. Once your dog regularly paws your hand, increase duration and difficulty. Praise/click and treat your dog once they hold their paw on your palm longer.
When your dog paws at your hand, start slowly and build up the time. If you want to click, praise, or treat your dog, wait until its paw is on your hand. It's important to time when you treat and praise your dog so that they know what you want,.
Before you click, praise, and treat your dog, ask them to hold their paw on your hand for one second. It won't take long for your dog to figure out that putting their paw on your hand is what gets them the food.
Introduce your preferred verbal cue when your dog regularly places their paw on your palm. “Shake” is the most typical cue, but use any word. Hold out your hand before your dog's paw touches, say "shake," then praise/click and treat.
You can flatten your hand sideways and ask your dog to shake with a verbal signal if they consistently succeed at this level. Give your dog a click and goodie when his paw touches yours. Unless your dog shakes, they're not ready for this level.