Yes, although the data needs to match the structure that the store is expecting.
With this in mind, the easiest way to import is to do an export first of all so that you get a spreadsheet with all of the necessary columns in the right place. You can then enter the information into this sheet and then import when you are finished.
To export the product sheet, you will need to click on Products and then Import and export. Click on Export to export the product list.
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