You can easily change your email account password from your web hosting control panel, cPanel.  The first 2 steps are the same as when you create a new email account:

1) Login to your web hosting control panel (refer to logging into cPanel tutorial here).

2) From your web hosting control panel, click on the "Email Accounts" link/icon:

3) Here, scroll down the page to the list of your created email accounts.  Click on the "Change Password" link:

The screenshot above actually shows the screen right after creating the email address "test@sample-website.com", with the email account confirmation message, and then right below that the list of email accounts including the one just created.

Clicking on the "Change Password" link will display the Change Password form:

Fill in your new Password in the field provided, confirm your new Password.  Again like in the Create Email Account form, you can click on the "Passsword Generator" button to use this tool to create a password for you to copy/paste into the Password fields.  Then, click on the "Change Password" button to complete updating your email account password!