why I cannot use socket.io module if install globally

I just want to ask why I cannot use the module of socket.io if I install this globally, I am new in socket.io, I tried to execute this command "node install socket.io" to this C:\Users\username>node install socket.io but then after It installed and run my app.js.I get error cannot find socket.io module..but when I run command "node install socket.io" where my app.js is located it works fine.

Thank you in advance.