WooCommerence supports four product types which are: Simple product, Grouped Product, External/Affiliate product, and Variable product.

A Simple Product is just that.  It is a single product, can be downloadable,  with a Regular Price($)  a Sale Price($).  To indicate that it is a downloadable product, click on the Downloadable box that is just under the title Product Data.

On a simple product you can set a sales price along with the schedule.  Just enter the sales price and then click on Schedule to bring up  field to enter the dates.

When clicking on the schedule you will be presented with a window for entering the dates that the sales prices is valid for.  Clicking on the calendar icon will bring up a calendar. Just click on the desired date and the field will be populated.