If you need to change your backup settings, such as FTP credentials or backup frequency, simply go to your backups dashboard and click on the website and then Settings:

change backup settings

Edit the settings, re-enter your password and click Save.

You can change your backups start times by going to your backups dashboard and clicking Settings -> Other Options

change backup start time

If you are still not sure what do, please feel free to open a support ticket with the Sucuri team.