With Auto Sync, you only need to add product information once.
To find the Auto sync setting, go to your store page that you can find on the sidebar under the 'Connect' section.
Once on your store page, go to the 'Products' section and click 'More' to see your Auto-sync setting.
If you are showing our shipping rates at the checkout page of your store, we recommend that you leave auto-sync ON, as our platform will be able to provide accurate dynamic rates until after you have shipped each item at least once.
The second option ('Automatically update my products when I edit items while creating shipment'), instead, will allow every change carried out at item level to reflect on your products list. For example, if you change the dimensions of an item before shipping, this feature will automatically update the dimensions of that item in your product list. And the next time you will sync an order containing the same item you won't have to re-insert the right dimensions again!
Note: You can also add all your products via file upload, to learn how to do so, please have a look at the following related article: Add Products Via File Upload