More specific questions would help. You mean getting into that area?
I worked in the sector but not directly with the young people but I know about support/mentor type work in the voluntary sector.
Your starting point needs to be experience working with young people in general, volunteering in a youth group setting is usually the easiest starting point. But you'll also want to see if there's any charities working in the area near you and get experience there, it'll be harder for you to get to work directly with the young people so anything that gets your foot in the door since even doing admin will help you learn.
You are then going to want to go into support work. For this you want a qualification in social care, it's not strictly required to get started but you'll struggle without it. Aim for a level 3 diploma at least. In the organisation I worked in a lot of the support staff had degrees (a few had masters), those who didn't were typically more middle aged and hence very experience having worked their way up from more basic support work. These are people in jobs around £24k and degrees were in things like psychology, youth work and social work.
It's a fairly specialised area so it might take you a few years to work your way into it.