To reset/change the password for your email address created in the control panel, you need to first log in to your control panel using the credentials you received in the email "Your new web hosting account". Once you're logged in, go to the section called Email, which you can see here:
In the "Email" section, there is an icon with an envelope, and next to it, it says "Accounts". Click on it. Once you're in there, it will look like this:
Scroll down until you find your account, and on the same row, there will be a blue text saying "Manage". Click on it, and you will be able to enter your new password.
You can also generate a new random password by clicking on "Password Generator" and then clicking on "Use Password". If you don't want to generate a new password, you can enter your own and then click on "Change Password". You have now changed your password for your email address.
When using the password generator, you will receive a completely automated password. Use this only if you want the most secure password possible. Remember to write down your password so you don't forget it!