How can I know if the installation of code snippet is correct?

1. Enter the home page of your store

2. Click on the browser menu -> View -> Developer -> View Source (for Chrome, other browsers also have a similar setting to view coding)

3. If you can find a similar coding (highlighted in red color), you're done! 

p.s if you find that Facebook doesn't update your social image, clear cache stored by Facebook in  Facebook Debugger. Just press the "Scrape Again" button for few more times though you may find it not responsive.