The Share Buttons plugin will add Facebook, LinkedIn and Tweet share/like buttons to the bottom of your form, so users can share it. Note: This is doesn't share their submission details, just the message you set and the link to the form. This is good for viral forms, such as contests. To add the Share Buttons plugin, go to Settings > Plugins and click the Add button next to Share Buttons.
This will add a Share Buttons tab to your Settings under the Plugins tab on the left and automatically take you into the Share Buttons settings. You can change the default Share Message users see when clicking on your Share buttons in the settings.
The Share Buttons will appear at the bottom of the browser window on your published form as shown below: