To import a new brand from your backend follow these instructions:
1. Go to BrandsSync > Import
2. Use the menu to filter the products you want to import (you can select a brand, a product category, etc.). To select only products not previously imported from the 'All products' menu select 'Only not imported' and click on 'Filter'
3. Select the check mark next to the products you want to import
4. From the 'Group actions' menu select 'Import'
5. Click on the 'Apply' button
After these operations the products will be added to the import queue.
You can check the progress of the import from BrandsSync > Status.
To view a tutorial go to this link or watch here