Hi @ahussein1194 ,
and welcome to the ROOT forum!
You can read ROOT files in a number of ways, see e.g. this post.
The simplest is probably to use RDataFrame (docs, tutorials).
About getting the charge of a particle from its PDG ID: doesn’t that tell you what particle it is? So e.g. if you know it’s an electron, you know what charge it has. I’m not a HEP analyst though 
Cheers,
Enrico