Try to see your strengths in relation to what energizes you. Something is a strength if: 

It's difficult for us to see our own strengths, but people around us (friends, coworkers, family members, mentors) will most likely see them clearly.

The ones you are most proud of. 

• Start by taking a class or reading online tutorials. 
• Think about the constructive criticism you've received.
• Develop related skills. Learn something that will make you better at your core strength, taking into consideration your long-term plans.
• ...