You cannot insert your widget code on social networks. However, you can easily share it.
To do so, create a widget, and then click on the "link to share" button found above your widget code. Copy the link to share your widget in a status, post or message. Wwhere you'll see the ebook cover and its data. Users who click on it will get to a page where it'll be a piece of cake to complete the purchase (the earnings of which will go to you).