A perfect way to measure the success of your Facebook advertising campaigns is to add your Facebook Tracking Pixel to your landing page.
How to add Facebook Tracking Pixel to your page:
1. Go to your page's Settings and click on Analytics;
2. Select Facebook Pixel;
3. Paste your Facebook Pixel Id in the designated field;
4. Facebook pixel tracks page views by default so a really easy way to track other conversions(like form submissions) is to add the pixel to a Thank you page and redirect your visitors to it after form submission.
That's it, now you can track your results with your Facebook pixel: