Log into WHM

In the left-hand sidebar, expand the Account Information section

Click Password Modification

Select the account name or username in question from the available options in the Account Selection section
Note: resetting the password for an account resets the password for all related services that customer uses, like FTP, MySQL and WHM.

Type a new password in the Password Entry section

Re-enter the password in the Password (Again) field

Click the Change button near the bottom