From Products Menu, click Import/Export, then click XML Product Import
On this page (as well as this one), products can be imported in bulk. This page requires those products to be in an XML file, formatted like this sample file.
When an import file is processed, the software looks at each entry and compares it to existing products in the storefront. If the SKU of a product in the import file matches an existing product, that existing product is updated with the information from the new file. If there is no SKU match, then a new product is created with that information.
To import a new product list, use the Choose File button to locate the import file, then click Upload.
Once the file has been processed (this can take a while if it is a large import file), the screen below will be shown. It is a good idea to click the View Import Log link and make sure that there are no errors showing. If everything looks ok, click the Click Here to Accept Import button to complete the process. If there are problems showing in the log file, or you wish to cancel the import, click the Click Here to Undo the Import button.