Please note that this option is only available for cPanel accounts. Please follow this article if you are using Website Panel.
For those using cPanel, you first need to log into your customer zone
Once logged in your client area, you can click on Services.
Under My Products & Services, you can search for your domain and click on Manage Product.
On the Manage Product page, you can scroll down on that page where it says Manage Account and click on Email Accounts.
On the Email Accounts page if you now scroll down to the bottom you would be able to view all your email addresses.
From here you can now click on the Change Password button.
The Change Password screen will come up, where you can now enter the password and repeat it.
Click Save Changes to apply the new password.
You should see that the password has been changed successfully.
If you struggle to change your account password following the above article, please contact firstname.lastname@example.org for further assistance.