How do I see my seed phrase or an account's private key?

Open Settings, then your account, and choose Seed phrase or Private key. Both ask for your password again first, even though the wallet is already unlocked, and both are shown masked until you tap the eye.

The seed phrase is the master key to every account in this wallet; a private key covers one account. A wallet imported from a private key has no seed phrase to show.

When you write the phrase down, write it on paper and keep it offline. Not a screenshot, not a photo, not a note that syncs to the cloud, not a password manager you access from the same browser — anything that reaches a screen or a server is something that can be read by whatever gets into that device or account.