Configuring custom file

I’m using Grafana in Windows, and I would like to configure Notification chanels. I am configureing the SMTP section in the custom.ini file, but when I try to save the file, I get an “Access Denied” error message.
Am I completely missing something?

How did you install Grafana on Windows - did you use the windows installer or another method? It should be the grafana.ini file so wondering if you have installed it manually?