Having trouble changing global permissions

I'm really new to R and RStudio. I downloaded RStudio on my macos, and I'm trying to alter global options of Packages, but I'm always receiving "Permission Denied" when I tried to alter the global options. I tried to find the ~/.config/rstudio folder but also failed. I don't know why there is no rstudio under my .config directory. How can I make changes to the permissions of RStudio so that I can make changes to global options?