fukein bonsai

Forgive me if this has been covered before. Please, could anyone help tell me what’s going on here (see pics)? About 4-5 days ago I noticed some of the leaves on one side had turned v dark (almost black). I initially thought it might be sun burn - Id left it out too long in the sun one...

I've had the tree for about two weeks now, and I have been misting the entire tree every other day. I assume I was under watering it, given the amount of sun it gets, which I would consider full sun. Also, when the tree arrived, the leaves were covered in white spots. How do I get the leaves to...