Satou is good at singing.
Do you know any princes who are good at using olive oil?
I’m good at making funny faces.
Think of someone holding out their hand. This is average. Things rated below the hand are things you're bad at. Things rated above the hand are things you're good at.
Both of these kanji use on'yomi reading, though 手 uses an on'yomi reading you didn't learn with the kanji. It's a rare reading, so it wasn't included (and we just have to deal with exceptions like this as we go along). To remember the reading for this word, here's a mnemonic:
What are you good at? You're really good at taking Jourm (じょう) to the zoo (ず). No one else can take Jourm to the zoo, he gets mad and throws them into the animal enclosures. But you? Jourm trusts you.