kws50:
How do you activate them if opening them won't activate them???
You wear the apparel to "activate" it. Open your profile in game and choose edit apparel. Click on each piece to learn which attributes it enhances. When you accumulate enough of the same apparel, the item flashes "upgrade", you pay with coins to step that piece of apparel up to the next level.
Basically you choose a sponsor, then play head to head coin games for coins and boxes of apparel.
Sponsored play is free every 6 hours for 30 min or you can pay credits for extra play. Level 10 is maximum for all pieces. The SE hat will lengthen driver only for example and always a good one to advance.
There is a nice apparel how-to guide if you search.
Apparel is not allowed during ranked play.