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.
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.
Let me show you how to add a Google account to a Samsung Galaxy SIII so you can read you Gmail email, download apps from the Play Store and synchronize you Google Documents.