You will receive an email with instructions to follow to reset your password.
Skyward Family Access - Reset Password
Passwords do expire every 60 days.
I would suggest you set a Calendar Event/Reminder to repeat every 45 days to remind you to change your password so you do not get locked out.
You can ONLY change your password from the web version of Skyward. There is a mobile app version for Skyward but you cannot change your password using the app.