Upgrading is only available online. The first step to getting this achievement is raising at least $8,000 by competing in online events. Next, you'll want to go to your online garage, choose your Alfa Romeo Giuletta Quadrifoglio which is given to all players, and then select the "upgrade" option. You will be brought to a menu with a few different parts that you can buy, as well as some bars that show the effects of these parts. You'll want to purchase upgrades until your car goes from Tier 1 to Tier 2. You will be given a message that your car has changed classes, and you will unlock the achievement. It is recommended that you take at least one part off to bump it down to Tier 1, so that you can use the car online for the other upgrade related achievement.