In developing growth mindset, first he must know his purpose why he needs to grow his mindset.To develop a Growth Mindset you must:
Embrace your weaknesses
Know that Challenges = opportunities
Use your learning style
Stop seeking approval
Focus on the process
Cultivate a sense of purpose
Choose to learn well not fast
Reward efforts + actions
Constructive criticism
A positive outlook in life is what he needed. He must not be discouraged.