Hi,
besides @marlon.brade’s excellent suggestion, please see this post for a list of interfaces that you can use to read ROOT data – things should work the same for Delphes TTrees as for other TTrees.
You can also search the forum for other posts about Delphes.
If you share the code you have so far and what errors you are encountering we might be able to help further.
Cheers,
Enrico