Yes you can. The step-by-step solution to this problem is shown below.
Changing a User's Password
Step #1: Log in to the system as the "root" user.
Step #2: Assume the user's login account was "fred". At the command-line prompt, type "passwd fred".
Step #3: The system gives you the option of (1) Picking a password or (2) Having a password generated for you.
In this case you will probably want to select "1" to pick your own password. Enter "1".
Step #4: Enter the password two times (the second time is for verification).
The user's password has been changed.