1.  Create the product in Booklog.  Make sure to click its "Electronic" checkbox

2.  On the website, visit the View File Downloads page, and add the file to the Downloadable Files library:

                                          
Then:


                                
                
3.  Once you have added the file to the site, you can visit the product and attach the file to it.  Click the product's Edit tab, and Features sub-tab:

                                 

4.  Add the File Download Feature:

                                 

5.   When adding the Feature, make sure to specify your SKU


                                 

                ...use the autocomplete field to locate the file you uploaded:


                                 

                ...uncheck that it is a Shippable product:
                                 

                ...and click Save Feature