Well, here are some problems I see:

1.) customer.addAccount() takes an int as its arg, but you tried to send
it Account objects.
2.) customer.getAccount() takes no arg and returns a double (I am sure
that is not what you want).
3.) You are missing an opening bracket at these lines:

if (account instanceof CheckingAccount)
account_type = "Checking Account";
}

It should be:

If (account instanceof CheckingAccount){
account_type = "Checking Account";
}


There are other errors as well, but since the compiler hasn’t found them
yet, I will let you see them when they arrive. Part of the hardest part
of programming is debugging, as you are undoubtly now learning. Stick
with it though and it will make sense.