The installer asks you to create the first account. That account is the master admin: it can use the ACP and change everything. Log in with the user name or email address and the password you chose there.
Accounts created after it are normal member accounts.
This works for every account, the master admin's included.
Check your spam folder. If your site can't send email at all, the reset email can't arrive either: see Email Support for setting up email.