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If you want to reset your HESK password, you can go to the Script Installer, select Installations, select the orange pencil next your HESK installation, then look for the Admin Account section.
Enter your Admin account username, then enter in the new password you want to set. Then, scroll down and click Save Installation Details.
If you did not use Softaculous to install HESK, you can refer to this website to help reset your Admin password.