To change your password, Studio first checks your current one. You find this under Password in Settings: tap your name at the bottom of the sidebar, then Settings. On a phone, tap the menu button (≡) at the top right first.
You may also see, when deleting your account under Danger zone:
"That password is incorrect."
"Type your email exactly to confirm." (for accounts that sign in with Google)
What to do
Re-type your current password carefully.
Forgotten it? Tap your name at the bottom of the sidebar, tap Sign out, then tap Forgot password? on the sign-in page.
For Google accounts deleting the account, type your email exactly as it appears under Email in Settings. It is also shown, greyed out, inside the Your email box.