You can simply upload your products straight to your form through creating a 'Products' type question and importing a CSV file that contains your products and their details.
To do this, click on the configure icon on the right-hand side of your 'Products' question. This will open your configuration settings, next simply click the products tab, from here you will see in the top-left corner the option to export and import.
Here you can simply click on the import and choose the file you want.
Note: The set-up of your CSV file must match ours - for a template simply click on the export and download a CSV file to use as a template.