How to schedule a weekly backup of your data
This is probably the most important step you can take as a Salesforce Administrator. The Weekly backup service will send you an email that contains a link to the Data Export section of Salesforce, giving you an opportunity to download the data to a local hard drive.
We strongly recommend that you save that file to a location that's backed up regularly, such as a network server or Dropbox.
Select when you want your backup to happen. Typical wisdom is do things in the middle of the night. Don't do that. Schedule your backup to happen when you are most likely to be sitting at your desk when the email arrives. Remember, you only have 48 hours to click the link so you'll have the best chance of not forgetting if it happens during the business day. You shouldn't have any slowdown of your instance while the data is being downloaded for backup.
Pick an end time that's far out in the future.
When complete, you will receive an email.