All of this is managed from My Profile → Security.
Change password
You are asked for your current password, the new one and its confirmation. The security policy is the same as at sign-up: at least 8 characters, with an uppercase letter, a lowercase letter, a number and a symbol.
Active sessions
You can see every open session — device, browser, IP — and sign out of all sessions except the current one. Signing out other sessions asks for your password.
Delete account
This is irreversible. Before doing it you must have no balance left in your wallets; the app warns you. It requires confirming with your password.
Before any of these sensitive actions, the system may ask you to re-enter your current password as an extra confirmation.