From the off there is one topper unlocked, the 'Portal - Cake'. You can equip it from the Garage under 'Toppers' (See Solution for Grease Monkey in Rocket League
for more details on how to apply)
Once your car is applied with a topper head into exhibition mode and setup a 1v1 match with no bots, which means you'll be playing alone. Now simply score 3 goals and this achievement is yours.
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