For this achievement you'll need to earn one of the many Medals under the Stats and Awards section. Here you can see the many objectives needed to unlock a Bronze, Silver, Gold, and Onyx Medal. For this achievement you'll only need to unlock the earliest medal form by performing the necessary actions and then equip it. You'll pop this 5G achievement.
NOTE: VIP Season Pass owners will automatically unlock the VIP Medal after loading up the game for the first time. This is how I earned the achievement!
If you don't have the Season Pass the quickest way to earn this achievement is by playing one match of Overrun. After which you'll earn the "They're Coming" Medal.