Not able to access after I updated erpnext

Install / Update Setup
1

I followed the the steps listed out on this page - ERPNext Upgrade to Version 5 · frappe/erpnext Wiki · GitHub
The whole updation was successful but now when I open the site it throws an error.

ERROR
502 Bad Gateway
nginx/1.4.6 (Ubuntu)

2

Try bench setup production

3

how to do that? I would request you to please tell me in detail as I have little experience as a developer

Thanks