How do I get a gmail account on my HTC Cha Cha? 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.

THese links might help - SuperDroidROM for ChaCha // HTC ChaCha forum on XDA