In order to change the password to your FTP account you would need to firstly login to HELM.
Once you are logged in you should see something like this:
Click on "FTP accounts" to see the list of accounts that was created.
Depending on the access level of your account you might see something like this first:
Click on "domains" first and select the domain in question. You should see the FTP accounts option now.
Edit the account by clicking on the one in question:
Change the password to the one you wish to use and confirm the password in the field below it.
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.
You could use the password generator to assist you with this.