Before importing products into D-Tools Cloud, first you will go to SI and export your products.
 
Within SI, go to the Project Editor, click the Tools tab and you will see the Export/Import options in the ribbon:

When exporting you will choose to export just whatever Items you have selected, or you can export all Items:

This will open the Export Items to CSV File interface. Select/deselect the columns you want to export, or just go with the defaults. Note, not all columns will map to a column in D-Tools Cloud. When finished, click OK. 

Now you can import the file into D-Tools Cloud. Map up the headers of the columns you want to import. D-Tools Cloud should be able to map up as much as possible for you here. Next match up the brands and categories. Finally you can review and import.

Learn more about importing products here