You just bought Nexus 4 and you don't know anything about Android operating system, so I will guide you through literally first steps on this great phone.
Pretty simple and useful tutorial, where you will open a random photograph with smoke and convert it into something really not friendly for our environment.
If you want to receive your Gmail emails, synchronize and backup your contacts, calendars, media or to simply download an app from the Play Store, you need to add your Gmail account on the LG G2.
