You can reset both the Enable and Telnet passwords for the Cisco ASA 5505 through the Cisco Device Manager.
You cannot reset the password if you forget it. If you forget the firewall password, you must reprovision your server (more info).
Depending on which Cisco ASDM version you have installed, several options might display. If so, click Run ASDM Applet.
Your browser must have Java enabled and allow pop-ups from your firewall management IP.
Clicking Reset discards any changes and causes the panel to revert to the last saved information.