نصب webpack بر روی مک

سلام دوستان ، می خوام روی سیستمم webpack رو نصب کنم (MacOs)
و این کد رو میزنم npm i -g webpackولی با این ارور بر می خورم
باید چیکار کنم؟؟

    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: '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).

    npm ERR! A complete log of this run can be found in:
   npm ERR!     /Users/pouriahadaddi/.npm/_logs/2018-09-30T05_55_12_812Z-debug.log