Update or Change Juniper User Password via CLI

Login to the switch
Entering configuration mode (configure)
Edit system login (edit system login)
Edit user (edit user )
Set the Password (set authentication plain-text-password)
Enter the password (New password: type password here / Retype new password: retype password here)
Commit and save the changes (Commit)

configure
username@sw01> configure
Entering configuration mode
edit system login
username@sw01># edit system login
{master:0}[edit system login]
edit user
username@sw01># edit user
{master:0}[edit system login user ]
set authentication plain-text-password
username@sw01# set authentication plain-text-password
New password: type password here
Retype new password: retype password here
Commit