Hello,Sanjay!
If you want to modify the theme core files,
You already have all the rights.
You just need to:
Log in to your hosting space (server) via FTP client.
Then, on your server, find the agama-pro folder in the theme folder
(path should be this: … / wp-content / themes / agama-pr.o /), and
change the theme as needed.
Each file is there and can be edited
I suggest you make the child theme first, then modify the theme, because once when we update the theme every custom theme modification will be overwritten.
Best Regards