What this screen is
Your fixtures, in whatever calendar you already use - the one on your phone that reminds you about everything else.
Subscribing
Press Subscribe and copy the address into your calendar app. It updates by itself: a match that moves, moves in your calendar within a few hours without you doing anything.
Choosing what goes in
You can leave out competitions you are not interested in. The layers are yours, and changing them changes what your phone shows from the next refresh.
If nothing arrives
Calendar apps refresh on their own schedule - Google usually every few hours, and there is no way to hurry it from this side. If it has been a day, check that you pasted the whole address, and that you used subscribe rather than import: an import is a copy taken once and never updated.
Stopping it
Revoke makes the address stop working for good. Anybody you gave it to sees nothing after that.