Try looking through this thread here. This was the post ATA made when they released this feature. Also, link to the PIMD general questions thread for reference here.
On the left of your homescreen under the phone The icon with a picture of a blonde girl with a gold leaf laurel behind her. Press it. That's the list of your extracurriculars.
What is the Extracredible XC though? Can't see it. Just "Live Fabulously", "Soak up the Spotlight" and "Collecathon." Asking because of the Story Pass
These were new XCs that were added, the original ones in the post may have been removed at this point, I forget which ones are active. You’ll see it eventually, they change every hour or so. The Extracredible XC is the XC where you are rewarded for spending ECs, i believe.