$STUFF rewards are not automatically distributed.
$STUFF rewards will be available for redemption on a one-Epoch lag cycle. Essentially you can expect to have your $BOOK rewards available five days after the ADA for the Epoch is paid out. Navigate to https://rewards.stuff.io/ to view and claim your $STUFF rewards balance.
You do not need to claim your rewards balance after each epoch; your $STUFF will automatically accumulate, and you can claim it anytime without penalty.