I live in China and when I go to Settings > Accounts it's not an option to add a Gmail / Google one, is there any software I can download ?
You can manually add a Gmail mailbox using IMAP in the separate Email app.
As to adding a Google account to sync your contacts and calendar, unfortunately a great many of Android devices obtained from China have this "issue". The best course of action is to flash a firmware meant for the same device, but from a different region.
As to registering a new Google Account (Gmail Account), you can do it on this page: https://accounts.google.com/SignUp
As to how to add the Gmail account to your phone, you can do it from the Accounts & sync menu: