In order to change the password to your FTP account you would need to firstly login to cPanel.
Once you are logged in please click on FTP accounts that is found under the "files" section
You should be redirected to a page where it will show the list of FTP accounts that was created on this hosting space.
Click on Change Password next to the account in question and change it to something else you prefer.
Please note that it is always best to use a strong password to make it difficult for unauthorized persons to gain access to your website's content.