Publishing products is never been so easy. Access the store manager by the link. if you visit there for the first time you need to create a store with the proper details.
Follow the bellow steps carefully
Hover Products option and click Add New
Check The Virtual & Downloadable option
Create your Product Title
Set The Price. Set Sale option if you want to put your product on sale
Add a short Description of your product
Add you products Display Image
Select the Categories whitch best match to your product
Set appropriate Tags
Click Downloadable tab from the black area
Set your file name
Upload your product file
Finally Click the Submit for Review or Submit option