Harnesses are safe alternatives to collars for taking dogs on walks. Putting on a puppy harness is relatively simple--the hardest part will be trying to control the wriggling puppy who is excited to go outside. There are several different types of harnesses, but they all work basically the same way.
Get your harness and stick it in your pocket when approaching your puppy. The less you excite your puppy with the sight of the harness, the easier a time you will have. Plus you're teaching it skills for the future, so start by making the process simple and as controlled as possible.
Make your puppy sit, if possible. Hold the puppy between your knees, face out, to help control wiggling. Give it a treat.
Pull the harness out of your pocket. If it's a traditional harness, you'll put the neck loop over the puppy's head, and one leg through the front leg hole.
Click the belly band together across the puppy's back, and the harness should be on correctly.
For a step-in or vest harness, the dog's front paws go right into the two front leg holess. Then pull the two side straps across the back of the dog, and attach at the spine. Easy!