Gather up your halter and make sure the lead rope is attached, with everything untangled and ready. Holding the halter by the head piece, place it in your left hand and place the lead rope in your right hand. Approach your horse on their left side with a relaxed body language and low energy
Place the end of the lead rope over their neck. This is the first thing you do because if the horse begins to walk away, you can easily stop them by simply reaching underneath the horses neck and grasping the length of rope. Untie the head piece knot and hold the nose piece and the head piece length of the halter with your left hand.
Pass this underneath the horses neck. With your right hand, reach over the horses neck and grasp the head piece length of the halter.
Guide the nose piece of the halter onto the nose of the horse with your left hand, whilst still holding the length of the halter with your right
Secure the halter - see how to correctly do this by looking at my other article 'How To Tie a Rope Halter'. Many people try and put the nose piece on a horse first. But if the horse pulls their head up, they can easily get out of the halter. You also have to somehow then get the end piece over the horse's head. Many people will try and fling it over, which is quite hard to do, and which could also unsettle the horse or end up hitting either you or the horse in the face