Do I need to do something before using this app?

Yes, please remove your Facebook Pixel ID from the Facebook sales channel Shopify app, or the Preferences Page on your Shopify Store if you previously added it in there, and remove it from any other pixel tracking app you might have previously used. You will need to use only PIXELFY to manage your Facebook pixels. If you use other tools at the same time, you will have inaccurate reporting