To sign in, you need to have a Google Account. It's not necessary to have a Gmail in order to have a Google Account.
In order to sign in of Orkut Mobile App, just follow these steps:
- Open Orkut Mobile app
- If it is the first time you open, you'll be requested to select one of your Google Account stored in you Android device.
- Authorize you app's access.
Tip: Learn how to add more than one account to your Android phone.
If you don't have a Google Account, you can sign up now.