Settings is not in the list of tools in the sidebar. Tap your name at the bottom of the sidebar, then Settings. On a phone, tap the menu button (≡) at the top right first.
What you can change
Profile: your Name. Tap Save profile. Your Email is shown here and is used to sign in.
Reminders: turn Email me posting reminders on or off.
Appearance: Dark, Light or System, which follows your device. The same choices appear when you tap your name.
AI usage: how many writing requests you have used today.
Password: change it, or set one if you sign in with Google.
Danger zone: delete your account.
Your plan, credits and payments are in Plan & credits. Tap the Credits box at the bottom of the sidebar, or Plan & credits in the sidebar.