Welcome to the forum DeSilva!
The ebst way to learn carnatic (or any music) is through a teacher.
For carnatic it is more so, because of the intricacies that are hard to document. I suggest you take vocal classes. That will surely help you learn guitar, and most of all, improve your understanding of the music.
Sites like karnatik.com, musicindiaonline etc have some carnatic lessons you can follow. This board is better at answering specific questions.
Hope you have fun learning to play the guitar. good luck!
Aadalaam Vaa, Paadalaam Vaa, Kondaadalaam Vaa
Engum Endrum Pongidudhe Inbam, Inbam Pozhiyude