This is an awkward trophy to start with as you need to get a Certified item drop post game but seeing as they are random you could be playing for a while before you get one. A certified item looks just like the regular item but it does have its skill title showing too.
When you do unlock one go to your garage to customise your car and add the new item. I had two, both toppers. Take note of the criteria to increase its level.
I had a Striker graduation cap which required 'shots on goal' and a Sweeper tiara who required 'clear balls'. There are other different criteria you might get.
With both of these I had to reach a target of 50 to increase the first level but reach 200 to get the Veteran status (at the time of writing I have only increased the Striker graduation cap to Veteran). You can check the progress in your garage if you select customise car and go to the toppers section.
The games you play must be done online (no exhibition matches) but can be done in any of the modes. I played Hoops for the shots on goal and football for the clear balls.
Once you reach the target the trophy will pop as soon as the match is over.