While other attributes of a user account can be edited in the New UI, changing a user’s password must be done in the Classic UI.
To change a user’s password:
Log into the Classic UI as an Administrator.
Open the Users tab: in the Features bar, open the Users and Groups folder and select Users.
Open the Manage User Information pop-up: either double-click the desired user; or select the desired user, open the Action dropdown, and click Edit.
Edit the password as desired.
Click the Save button.