Git BASH Install Problem

Trying to install GitBash on my laptop. After downloading and installing, your instructions say to:

1. Open the Git BASH terminal

2. Type:

npm install gulp -g

...and click Enter.

I can't find a specific Git BASH terminal on my computer after downloading. I tried running it in my Terminal app and got permission errors (see below). What am I missing?

checkPermissions Missing write access to /usr/local/lib/node_modules npm ERR! path /usr/local/lib/node_modules npm ERR! code EACCES npm ERR! errno -13 npm ERR! syscall access npm ERR! Error: EACCES: permission denied, access '/usr/local/lib/node_modules' npm ERR! { [Error: EACCES: permission denied, access '/usr/local/lib/node_modules'] npm ERR! stack: npm ERR! "Error: EACCES: permission denied, access '/usr/local/lib/node_modules'", npm ERR! errno: -13, npm ERR! code: 'EACCES', npm ERR! syscall: 'access', npm ERR! path: '/usr/local/lib/node_modules' } npm ERR! npm ERR! The operation was rejected by your operating system. npm ERR! It is likely you do not have the permissions to access this file as the current user npm ERR! npm ERR! If you believe this might be a permissions issue, please double-check the npm ERR! permissions of the file and its containing directories, or try running npm ERR! the command again as root/Administrator (though this is not recommended).