To change a user's password in Linux, you can use the passwd command. Here's how to use it:

1. Open a terminal window.
2. Type passwd and press Enter. You will be prompted to enter your current password.
3. After entering your current password, you will be prompted to enter your new password. When entering your new password, you will not see any characters on the screen as you type. This is a security feature.
4. You will then be prompted to re-enter your new password to confirm it.
5. If the passwords match, you will see a message that says "passwd: password updated successfully." If the passwords do not match, you will see a message that says "passwd: passwords do not match."

It's important to note that only the root user can change the password for another user. If you are not the root user, you will need to use the sudo command before the passwd command to change another user's password. For example, if you want to change the password for the user "bob", you would use the following command:

sudo passwd bob