In my experience of working with young people - confidence is not often a strong point. Oh they can pretend! Often clumsily attempting bravado and bluster. But real confidence is lacking.
Building it takes time and a little bit of skill. The main thing is they have to trust you. Trust that you won’t laugh at them. Trust that you won’t be disappointed. Trust that you are being honest with them.
Let them see your mistakes. Allow them to make them too. Let them learn that making mistakes is good thing. Not something to be mocked or angry about.
Give them space. Don’t watch over them when they are trying something new. Let them slowly come to you, and ask for help.
Most of all, if they aren’t enjoying learning a new skill or task, give them time. Most people resist ‘new’. If they are interested they will return. Just don’t compare them to other peers who have maybe stuck with something or picked something up quicker.
To help you unlock some of these points yourself, and better understand how to facilitate a mindset that will be open to challenging their conventions, here is some further reading and viewing…