As we explained in How to add a new product chapter, one of the options is to import them by using the batch import window. You can click the batch import button on your product page, click the 'Start Import' button from the right top corner and choose the first option, which is 'Add new products'. Please keep these in mind:

• You should use the template provided in the window.
• Do not leave Name, Brand and Category columns blank. The product will not be imported if it does not have any of this information.
• The first letters of the words will be capitalized. 
• Do not enter non-numeric information in the Product Cost column. The costs you enter will be imported with the currency of the panel.
• Do not forget to map all of the columns you want to import.
• You can change the names of the columns as long as you map them correctly.
• If two products have the same Name, Product Code, Brand, and Category the second product will be recognized as a duplicate and will not be imported. 
• If you want to add new URLs to existing products you cannot use this option please check here.

Here is a video about this process.