I bought a used x55ew, I can't log in username appears ADMIN I don't have the access pwd, is there a way to reset the device?
Note that your firewall went End of Life on 31 Dec 2015, which means that there is no longer support for this model.
This is a very old firewall, and may have known vulnerabilities.
Reset a Fireboxhttps://www.watchguard.com/help/docs/help-center/en-US/Content/en-US/Fireware/backup_upgrade_recovery/recovery_procedures_c.html
Firebox®X Edge™ e-Series Hardware Guidehttps://www.watchguard.com/help/docs/edge/10/v10edgehardwareguide.pdf
Firebox X Edge e-Series Quick Start Guidehttps://www.watchguard.com/help/docs/quick_start_guides/LEGACY/CORE_PEAK_EDGE/edge_quickstartguide.pdf
You need to register your firewall with WatchGuard in order to get a Feature Key, which will enable a number of basic firewall functions.
Open a support case (via the Support Center link above), select Customer Care, and provide the model & serial number. Then Customer care should provide you a Feature Key which you need to import into your firewall.
I must admit a morbid curiosity as to why you bought such an ancient firewall. The Edge series is quite old and has very outdated firmware. You may risk your internal network if you use it as a perimeter firewall to the Internet as Bruce noted.
I don't remember that far back, but some devices used to have the following default usernames and passwords:
Device Administrator role with read-write access
User name: admin
Device Monitor role with read-only access
User name status