You help someone when you give them what they need. You might help someone with their homework, or help someone build a fort. The man in the picture is helping the toddler climb the stairs.
A similar word to help is assist.
A yelp is a short, sharp noise made by a dog, often because they have been hurt. Anyone who makes a similar sound is also said to be yelping, for example "she let out a yelp of pain".
