Definitely take a look at the graphics
@Beman posted. I wish they wouldn’t sell those kits.
You’re going to want to upgrade his lighting, t5ho 10% or 12% ASAP. Light is the most natural and safe form of uvb for them. In addition you will want to add a multivitamin 2x a month. Use one with preformed vit A, not beta carotene. I use reptivite with D3. The calcium in the kit (no D3) is good for daily use. They should be fed only in the morning, as they need to bask to digest.
You’re also going to need a larger cage as he grows. You’re also going to want to add a LOT more foliage than what comes in that kit. Safe live plants are preferable, IMO, if you can get them.
Definitely stick around and ask questions, these guys can be sensitive and there is a lot of bad info out there, but they can also be super cool and rewarding. Making him feel secure (more foliage) and getting him the proper uvb, plus some time to settle in and he should eat for you. As for cage aggression, they aren’t cuddly animals. Some are never going to be happy to see you. Some get better if you move slowly and hand feed their favorites. They’re all individuals, but don’t count on having a friendly veiled or “taming” him. They are what they are!
Also, does he have little spurs on his back feet? Hard to tell from the pic. If not, he may be a she.
Edit: in a slow typist, so I accidentally repeated a lot of what Beman said! Whoops